Low upstream power levels

I have an ethernet cable ordered and will try that once it arrives.  I haven't tried bypassing the splitter yet.  I'm concerned that once I disconnect the current splitter to put the modem in that line, I'll have to reboot all of the cable boxes in the house.  It took me over 90 minutes to get them all configured the way we want them, and I'm reluctant to do all of that again since even if the splitter is the problem, removing it isn't the solution.  We need all of those cable boxes to be connected, so I can't keep the modem ahead of the splitter.

Xfinity knew we had 5 cable boxes in the house when they offered the internet service at this location (the other 2 connections on the splitter are terminated), but they didn't tell me I'd have problems with internet given this configuration.  I'm told there are "active" splitters but that they often create a lot of noise on the line that negates much of the benefit.  

It isn’t uncommon for a customer to have 5 cable boxes. It is likely the previous representative didn’t think there would be any issue when assisting with the internet. With the issues you are currently experiencing, it may be best to have an amplifier installed as EG mentioned. Could you please send our team a direct message with your full name and full address @user_1dhux1? Our team can most definitely take a further look at this issue. To send a "Direct Message" to Xfinity Support:

Click "Sign In" if necessary
Click the "Direct Messaging" icon or  https://forums.xfinity.com/direct-messaging
Click the "New message" (pencil and paper) icon
The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there
 - As you are typing a drop-down list appears. Select "Xfinity Support" from that list
 - An "Xfinity Support" graphic replaces the "To:" line
Type your message in the text area near the bottom of the window
Press Enter to send it.

I connected the cable modem/router directly to the line coming into the house (disconnected the splitter and all other connections). 

I also connected the laptop directly to the cable model via ethernet (disabled the wifi on the laptop).  Neither of those solved the problem.

But, I noticed a different symptom.

I am able to connect to cnn.com and google.com. But, I couldn't connect to any other site I tried (abcnews, nbc news, my e-mail, ...). 

I still don't have any WAN address in the configuration page, so I don't know how I could be connecting to some websites if I don't have a WAN address.

I also noticed that the upstream QAM power level was even lower when connected directly to the input line (not thru the splitter). Upstream QAM was only 23-25 dBmV when connected directly to the input line.  It was in the mid 30's when connected through the splitter.  

The only thing I have left to try is trying a different cable modem unit, but I have no reason to believe the unit I'm trying (Arris Surfboard G34) is faulty - it's a brand new unit - and it connected to at least two websites.

(I realize this is dragging out over several days.  I'm in a remote area, so I have to wait for deliveries of hardware to try different diagnostics. I have limited time each day to work on this.  And, disconnecting the splitter interrupted the television for the entire house, so everyone else was not able to watch the television while I was working on this.  Plus, I had to reboot all of the cable boxes after I reconnected the other lines to the input lines.)

Hello @user_1dhux1, thank you for taking the time to reach out on social media.  I understand your concern and want to help in any way I can. 

We can look into scheduling a technician appointment to install an amp for you. 

To access your account, will you please send us a direct message with your full name and complete service address to “Xfinity Support”. To do so, click on the chat icon located at the top right of this forums page.

Here's the detailed steps to direct message us:

• Click "Sign In" if necessary

• Click the "Direct Message” icon (upper right corner of this page)

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list

• Type your message in the text area near the bottom of the window

• Press Enter to send your message