wifi won't connect to honeywell thermostat 900

[stephenleccese]

I have a honeywell thermostat 900 which is connected to my wifi.  Comcast upgraded my system and installed a new modem. Since then I am not able to connect to my thermostat.  I have talked to Comcast several times and even had a knowledgeable comcast tech come to the house.  I have had many suggestions about a solution from both comcast and Honeywell.  I tried them all but nothing has worked.1

[EG]

Are you associating it with your home network's current WiFi broadcast name (SSID) and your WiFi network's current password / network security key ?

[stephenleccese]

Yes I am.

[EG]

If your  WiFi bands are combined, and 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;

https://www.xfinity.com/support/articles/change-wifi-mode-admin-tool-xfinity-xfi