90 plus two stage gas furnace, carrier one stage heat pump, Initial run testing confirmed correct operation of the primary mechanicals including the gas furnace with the blower and a carrier heat pump Multiple on and off cycles all produce the same results in both modes with the heat pump running and producing 101° of supply temperature and the gas furnace was producing 134 and climbing until the high stage gas pressure was reduced one full turn counterclockwise reducing the supply temperature and stabilizing it at 125° f. Resurface flame sensor and flush furnace condensate trap Cycle through all installation and pro settings of the nest thermostat, test run heat pump heat and gas heat (alternate heat mode) and confirm startup multiple times After a heating cycle shutdown the thermostat displayed a warning indicating reattach to sub base and connect to power for use. Furnace power is confirmed on and thermostat is intermittently working. Recommend homeowners contact nest tech sup