What should I do if my Honeywell T6 thermostat screen is blank or not responding?

If the thermostat screen is blank, first check the circuit breaker or fuse connected to your heating or cooling system and turn it on if it's off. Make sure the power switch on your heating or cooling system is on, and ensure the furnace door is closed securely. If the heating or cooling system isn't responding, check that you've set the correct mode (Heat or Cool), that the temperature set point is appropriate for your desired operation, and wait 5 minutes for the system to respond after making changes.