It turned out it was the plate behind the thermostat. The one the wires
get clamped into. But you can't find the plate available anywhere
because of supply chain issues. We had to buy a new thermostat.
So we DO HAVE a C wire, and it IS receiving power (verified today by my
HVAC tech). 3rd Gen Learning Thermostat suddenly off line. This started
yesterday. I'm charging it now, but this is not a solution. Note, I have
3 other Nests in the house, with ...
