Both our wi-fi enabled TV and our printer stopped connecting to the wi-fi last month. When I search for a network on both devices, nothing shows up even though our computers and phones are connected and the wi-fi is working. I have tried restarting the gateway several times and it still doesn't work. I can't seem to find a phone number for support and the Xfinity Assistant is no help. I'm beyond frustrated right now ...
The two WiFi bands have recently been combined into one with the Comcast gateway devices. Some devices get confused and don't know how to see / talk to combined bands.
If you are not using any Xfi Pods, you can try separating the 2.4 and the 5.0 bands and give them two different broadcast names / SSID's;
Associate the devices with the 2.4 or the 5.0 (whichever one works) band's SSID (broadcast name) and password.