Poor Upstream Power Level? And what does this mean: Critical SYNC Timing Synchronization failure - Failed to acquire QAM

@XfinityShan​ Dropped or unsuccessful connections and terribly inconsistent and frustrating usage is probably more to the point. At times--no specific time of the day--I simply cannot access web sites. I get "took too long to respond" errors or some sort of DNS related error, especially for .edu sites that I need to have reliable access to for teaching online. 

Sunday my cable connection was so poor that neither my iPad not my PC would let me sign in to things like Gmail; they simply would not accept my passwords. Later, when the connection was apparently better, I had no problems using those passwords or those devices.

I don't game, but I do stream content, I've never had a problem streaming from my PC, but my Flex device cuts out every time I use it, and I mean multiple times, like every 10 or 15 minutes sometimes.

I've run the Network Troubleshooter numerous times over the past week, and it finds no problems. God knows how many times I've reset my modem to get the Flex device to work or because I couldn't access web sites on my PC. I really don't know what to do. I've even tried using an R11 coax cable to connect my modem and still got the same Poor rating for my cable connection from my modem/router. Here is the latest Diagnostic report (4PM, 10/5/22); maybe it will tell you something:

Cable Diagnostic

Status: Poor

Action: 
[Upstream Power Level]
Try these actions (Click the Refresh button after each step):
1) Make sure the coaxial cable is tightly connected.
2) Remove any unnecessary splitters.
3) Replace any required splitters.
4) Contact your service provider for troubleshooting help.

Internet Access: Good

Downstream Status: Good

    Downstream Power Level: Good

    Downstream SNR: Good

Upstream Status:  Poor

    Upstream Power Level: Poor
    Upstream power is poor (51.3dBmV). The recommended level is from 30 to 50dBmV.

Current time: Wed Oct 05 14:58:26 2022

Startup Procedure
Acquire Downstream Channel: 507 MHz   Locked
Connectivity State:          OK       Operational
Boot State:                  OK       Operational
Security:                   Enabled   BPI+

Downstream Bonded Channels
Channel LockedStatus Modulation ChannelID  Frequency        Power       SNR   Correctables Uncorrectables     
      1     Locked     256 QAM      5     507000000 Hz     2.2 dBmV     42.5 dB     153     773
      2     Locked     256 QAM      1     483000000 Hz     2 dBmV     42.4 dB     24     126
      3     Locked     256 QAM      2     489000000 Hz     2 dBmV     42.4 dB     583     2214
      4     Locked     256 QAM      3     495000000 Hz     2.2 dBmV     42.5 dB     620     2290
      5     Locked     256 QAM      4     501000000 Hz     2.2 dBmV     42.5 dB     713     2618
      6     Locked     256 QAM      6     513000000 Hz     2.2 dBmV     42.5 dB     722     2526
      7     Locked     256 QAM      7     519000000 Hz     2.1 dBmV     42.3 dB     801     2580
      8     Locked     256 QAM      8     525000000 Hz     2 dBmV     42.3 dB     750     2745
      9     Locked     256 QAM      9     531000000 Hz     1.8 dBmV     42.1 dB     778     2853
     10     Locked     256 QAM     10     537000000 Hz     2.1 dBmV     42.2 dB     708     2347
     11     Locked     256 QAM     11     543000000 Hz     2.2 dBmV     42.3 dB     729     2427
     12     Locked     256 QAM     12     549000000 Hz     2 dBmV     42.3 dB     669     2298
     13     Locked     256 QAM     13     555000000 Hz     1.8 dBmV     42.1 dB     661     2168
     14     Locked     256 QAM     14     561000000 Hz     1.8 dBmV     42.1 dB     705     2163
     15     Locked     256 QAM     15     567000000 Hz     1.4 dBmV     41.9 dB     625     2631
     16     Locked     256 QAM     16     573000000 Hz     1.3 dBmV     41.9 dB     849     2976
     17     Locked     256 QAM     17     579000000 Hz     1.3 dBmV     41.8 dB     644     2377
     18     Locked     256 QAM     18     585000000 Hz     1.2 dBmV     41.7 dB     804     2660
     19     Locked     256 QAM     19     591000000 Hz     1 dBmV     41.7 dB     834     2788
     20     Locked     256 QAM     29     459000000 Hz     1.7 dBmV     42.4 dB     863     2361
     21     Locked     256 QAM     34     465000000 Hz     1.7 dBmV     42.4 dB     613     2263
     22     Locked     256 QAM     35     471000000 Hz     1.8 dBmV     42.4 dB     756     2423
     23     Locked     256 QAM     36     477000000 Hz     2 dBmV     42.5 dB     777     2968
     24     Locked     256 QAM     38     435000000 Hz     2.1 dBmV     42.5 dB     751     2209
     25     Locked     256 QAM     39     441000000 Hz     1.9 dBmV     42.6 dB     666     2452
     26     Locked     256 QAM     40     447000000 Hz     1.6 dBmV     42.5 dB     805     2815
     27     Locked     256 QAM     41     453000000 Hz     1.7 dBmV     42.4 dB     737     2425
     28     Locked     256 QAM     42     405000000 Hz     2.5 dBmV     42.7 dB     795     2462
     29     Locked     256 QAM     43     411000000 Hz     2.4 dBmV     42.6 dB     900     2615
     30     Locked     256 QAM     44     417000000 Hz     2.5 dBmV     42.6 dB     826     2412
     31     Locked     256 QAM     45     423000000 Hz     2.2 dBmV     42.4 dB     648     2291
     32     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0

Upstream Bonded Channels
Channel   LockedStatus  ChannelType ChannelID   SymbolRate        Frequency       Power     
      1       Locked       ATDMA      1       5120 Ksym/sec       35600000 Hz       45.5 dBmV
      2       Locked       ATDMA      4       5120 Ksym/sec       16400000 Hz       45.3 dBmV
      3       Locked       ATDMA      2       5120 Ksym/sec       29200000 Hz       45.3 dBmV
      4       Locked       ATDMA      3       5120 Ksym/sec       22800000 Hz       45.3 dBmV
      5       Locked       ATDMA      5       1280 Ksym/sec       39600000 Hz       51.3 dBmV
      6       Not Locked       Unknown      0       0       0       0.0
      7       Not Locked       Unknown      0       0       0       0.0
      8       Not Locked       Unknown      0       0       0       0.0

Downstream OFDM Channels
Channel   LockedStatus  ProfileID  ChannelID    Frequency       Power       SNR/MER    ActiveSubcarrier    Unerror    Correctable   Uncorrectable
      1     Locked     0 ,1 ,2 ,3     37     690000000 Hz     0.68 dBmV     41.1 dB     1108 ~ 2987     13309951     13194686     1033
      2     Not Locked     0      0     0 Hz     0 dBmV     0 dB     0 ~ 4095     0     0     0

Upstream OFDMA Channels
Channel   LockedStatus    ProfileID    ChannelID    Frequency       Power
      1     Not Locked     0      0     0 Hz     0 dBmV
      2     Not Locked     0      0     0 Hz     0 dBmV

Event Log
         Time               Priority     Description
Wed Oct  5 14:58:42 2022     Notice     CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:58:21 2022     Notice     CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:58:20 2022     Notice     CM-STATUS message sent. Event Type Code: 22; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:58:00 2022     Notice     CM-STATUS message sent. Event Type Code: 23; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:56:31 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:56:30 2022     Warning     MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:56:24 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:56:24 2022     Warning     MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:52:40 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:52:39 2022     Notice     TLV-11 - unrecognized OID;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:52:31 2022     Notice     Honoring MDD; IP provisioning mode = IPv6
Wed Oct  5 14:49:18 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:49:13 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:38 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:37 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:20 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:19 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:19 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:48:19 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:47:14 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:47:13 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:45:48 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:45:47 2022     Warning     MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:45:42 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:45:41 2022     Warning     MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:45:38 2022     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"]CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:23:10 2022     Notice     DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:22:48 2022     Notice     TLV-11 - unrecognized OID;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan  1 00:00:52 1970     Notice     Honoring MDD; IP provisioning mode = IPv6
Thu Jan  1 00:00:48 1970     Critical     No Ranging Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan  1 00:00:43 1970     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Oct  5 14:20:46 2022     Critical     Resetting the cable modem due to docsDevResetNow
Thu Jan  1 00:00:48 1970     Critical     No Ranging Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Thu Jan  1 00:00:43 1970     Critical     SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Tue Oct  4 12:27:29 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Tue Oct  4 12:27:29 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Tue Oct  4 12:27:27 2022     Critical     No Ranging Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Tue Oct  4 12:27:26 2022     Critical     Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Tue Oct  4 12:23:08 2022     Critical     Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Sun Oct  2 16:51:26 2022     Critical     Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

@

The PC is the only device hard wired to the internet. Everything else is WiFi. If there are any splitters, they're not visible. There's just one coax cable connecting the modem to the wall outlet.

@

Yes, both today and this past Sunday, I lost Internet access on my PC for several hours at a time, and the Windows network troubleshooter can't identify any problem.

Just now I've had to reset my modem to try to get my cable connection back, and I've had to struggle with my phone to get it to connect to my Wifi instead of Xfinity WiFi. The phone keeps claiming that my access point is temporarily full.

At this moment my phone is connected to my Wifi but my PC has no internet connection.