Upon inspection of Nest thermostat found to be flashing low battery. Removed thermostat from the wall and found to only have 4 wires installed. Went into attic and wired in a common wire for thermostat and check unit for 24 volt power. Found unit in attic to be ok at this time. Went to thermostat and added the common wire and installed the thermostat back on the wall. At this time thermostat is operating under manual mode due to no internet connection and low battery flash. 30 day labor warranty.