I just upgraded my gen 2 nest which has been working fine with my trane HVAC unit for 2 years.
I got the g wire e104 error. After talking to nest they sent me another one and did the same thing.
I put my gen 2 back in and everything works fine.
Same wiring, everything.
Nest support is saying I have a bad board or something like that.

When calling for heat or AC it sounds like the HVAC tries to start for about 5 seconds then it stops and throws the code.

Anyone have any idea what is going on? Why it works with gen2 and not 3. How to fix it or should I just forget about upgrading to the latest and greatest.

Wiring is Y1 G W1 C Rh

Thank you in advance.