Why does my T9/T10 Thermostat fail to power on?

Check your wiring to see if you have a C-wire. If you do not see a wire in the C terminal, refer to your Installation Guide / C-Wire Adaptor Guide to install using the c-wire adapter. Then, reset your thermostat by either gently pulling it off the wall near the base of the thermostat, allowing for one minute to pass, then placing it back on the wall, or by turning the service switch on your furnace/AC system off for 30 seconds. The device should recover within about 10 minutes.