Hello RASTA77,
We love seeing you here posting about your Nest thermostat showing a wiring report. I'd be happy to shed some light on the situation here.
The system might not provide enough power or any power to either the thermostat or a specific wire (so the thermostat can’t complete a circuit and show the code). To sort this out, please share with us a photo of your thermostat's wiring and gather the power readings in the Technical Info option appearing below the message code. Also, if you have a C wire installed, remove it and leave it disconnected.
Note: Turn off the power from your HVAC system at the breaker box before touching a wire.
Keep me posted on how it goes.
Regards,
Mark
