We have multiple nest thermostats controlling hotwater baseboard heat in the basement, a gas heater in the garage, and forced hot air via hot water air exchanger. Everything has been fine for five years. Now when the main house asks for heat, the thermostat shows "heating" with the target temperature (2+ hr), but the temperature "stalls". The nest app is showing "at home" and preheat is enabled. For example, currently it's 3p and 38F outside and 65F inside. The schedule called for 67F starting at 9a -- so it's been more than 6h.
