I was facing a similar problem with a a heat pump system, it turned out
i didnt not set orientation properly. I hope its the same with you. If
it is you can any of the
guide:https://support.google.com/googlenest/answer/9257086?hl=en#zippy=%2Cchange-t...
I dont know if there is anyone else facing the problem. But you need to
connect the other end of the black wire in to the C terminal on the
terminal block of the furnace well.
