Smart thermostat disconnects from new Surfboard due to "intersecting bands?" on G36

This is the written diagnosis:

Found systems infinity control was operating but not connecting to carriers servers for remote access. Tested with mobile hotspot and confirmed infinity control connected to carrier server without issue. The customers new modem must be preventing access. Mentioned to customer to reach out to there manufacturer of the cable modem to fix the issue. The modem has to have to separate channels 5ghz & 2.4ghz when connecting to Infinity Control as it can only operate through 2.4ghz.

What is the model number of your ARRIS device so that we can determine if it has a built-in Wi-Fi.  

It’s an ARRIS SURFboard Model G36 Wi-Fi Cable Modem, just a few months old. We bought it specifically to serve our iMac, printer, Chromebook, Samsung TV, etc., and the thermostat. It works well for everything but only occasionally with the thermostat.

Since you are experiencing intermittent connection on thermostat, I would suggest changing the security mode and monitor the performance.

Login to the web portal which is 192.168.0.1.

Once you logged in, select Gateway>Connection>Wi-Fi>select edit for 2.4G and change the security mode as WPAWPA2-PSK (TKIP/AES)

Thanks. I did as you suggested. I changed the setting, rebooted the router, and reconnected the thermostat to the WiFi. It verified the connection but will not connect to the thermostat’s server. They blame the router for not having parallel frequency outputs. That doesn’t make sense to me but I’m no expert.

You have tried with all the possible troubleshooting steps; I would suggest checking with thermostat’s manufacturer for further assistance Since all other devices are working without interruptions.

Thank you! I initially tried the manufacturer, and they said go to the installer, who charged us $110 to tell us it’s the router’s fault. We did have one of the installer’s reps tell us “This happens a lot. I don’t know what the problem is.” I’m tired of feeling like a pinball. It’s not that big a deal but—not that we don’t like the router and didn’t need one anyway—we purposely bought this model for the two bands. Oh well.

Thanks again!