This issue is caused by a power issue to the thermostat. There are a few different things you can check:
Some thermostats are powered by batteries only. Please make sure you have fresh, brand name batteries installed in your thermostat. If you need help changing the batteries, check out this quick video on how to change the batteries in your smart thermostat here.
If your thermostat fails to light up after changing the batteries, please call us at 1.800.PROTECT (1.800.776.8328) to schedule a service visit.
If your thermostat does not have batteries, then it gets its power from your HVAC system. Please make sure the HVAC system is has power, and ensure that you do not have any electrical breakers flipped.