The T9/T10 thermostat works best with the following network configuration(s): DHCP enabled, no hidden SSIDs or network names, and a 2.4GHz or 5GHz network. If you have a dual band network where your 2.4GHz and 5GHz are combined into one, log into your internet service provider account to split the network into 2.4GHz and 5GHz separately. If connection still fails, reset your WiFi router to clear out old memory and retry the connection.