I'm currently having the same issue. After numerous phone calls and chats, XFi app is now showing 4 devices connected but the other 20 are still a no go. I've done everything from resetting the router to forgetting devices within the app. Nothing.
I've also been dealing with this for the past couple of months. I've probably spoken to 8-10 customer service reps who are unable to address anything with this problem. Each time we speak, I'm told that this is going to be elevated to the "highest level". Not sure what that means, but I never get a return call or follow-up from anyone. Terrible customer service.
About a month ago, one of their reps recommended changing the network name/password. We did that and went back and reconnected our 12-15 devices. This seemed to work for the rest of that day, until we woke up the next morning and everything showed as "previously connected" and was no longer on the network....even though all of these things were connected.
Two weeks ago, I was working with someone who said to go in and "forget" all of those devices that were previously on the network and let them reconnect on their own. This also seemed to work for a few hours until these things started to drop off the network (at least according to the app). However they were still on the network. Now when I try to go this route, things that I have "forgotten" disappear and don't even show up on the conncected or previously connected list.....while they are still connected to the network.
Yesterday I spent over an hour on two calls to customer service. The first rep said that there was nothing that they can do and it would have to be elevated. They said they were going to transfer me to someone in that department, then hung up on me. I called back, and got a another CR rep. Spoke to them about the situation (even while having a ticket number, I still have to re-tell my situation every time I speak to a rep). She said that there was nothing that she could do, and that it would have to be elevated (now the 7-8th time that I've been told this) and to "keep my phone lines open" because someone would be calling back that day.....well that was over 12 hours ago and no one has reached out. That same rep said I would also get an email with step by step instructions on how to go in and find devices that have fallen off (the ones that were forgotten and never returned to either list), never got that either.
Bottom line, if one of your highly touted features is able to control/pause devices and manage your network through the app......it really should work.
Possible temporary "fix" to this problem...I too have been having the same problem with connected devices not appearing either in the xFi app or the gateway admin site (10.0.0.1). I have tried multiple gateway restarts, restored the gateway back to factory specs and reactivated, forgot all of the devices in the app, etc; all of the tips I've seen in these threads. FWIW, I stumbled upon what appears to be a temporary "fix" - on the Troubleshooting > Reset/Restore Gateway page of the admin site, if I hit the 3rd button down (Reset Wifi Router), the wifi goes down for less than a minute, but then magically most, if not all of the connected devices show up again in the Connected Devices list and in the xFi app. However, this does appear to only last about a day or 2 and I have to do it again. So clearly there's a problem that Comcast needs to fix, but hope that this helps.
Hi JPHTX. Thank you for creating a post on our Forum. I can assist with the troubleshooting process for your xFi connected devices. To get started, please send me a private message and include your full name and service address so I can assist you.