Hello Ravello,
Uh-oh! It's never ideal to have two Nest Thermostats go blank at the same time unless a power-related issue occurs, but thanks for letting us know about this so we can better understand what's going on. Let's jump in and bring them back to life!
First off, which Nest Thermostat do you have? Are the power breakers on, and do you receive power to your home? Are the thermostat displays seated properly? Are all the wires of your thermostats seated firmly in their terminals (with no loose or exposed wires)?
If you have the Nest Learning Thermostat, pull its displays and charge them via USB for an hour. For the Nest Thermostat 2020 mode, pull the displays and remove the batteries for at least 3 minutes before plugging them back in. Also, gather the power readings in the Technical Info or in the Equipment settings.
I'll look forward to your response.
Regards,
Mark
