Arrived on site to customer complaint the thermostats were blank. Both thermostats were in fact blank with no voltage. Removed disconnect to air handler to check input voltage. On reinserting disconnect- voltage returned to both thermostats and the zone board. Verified proper safety wiring, checked all wiring connections, verified voltage at both transformers, air handler control board, splices to safeties, zone board and thermostats. Cycled system through all modes of operation from the zone board and both thermostats. Verified proper damper operation. System is operating properly at time of departure pictures in CompanyCam.