I’ve switched out my old thermostat for a Nest E thermostat and according to my wiring setup it should be supported ( https://imgur.com/a/cdYJuIE ). I’ve had 3 separate HVAC technicians look at the setup and their testing is showing that the AUX heat is not activating despite it working when I turn on E(mergency) heat which is on the same wire. The thermostat clearly shows that AUX heat is on but the air is not being tempered and the heating coils are not turning on unless I manually turn on the E heat which is prohibitively expensive since it bypasses the heatpump entirely.

My setup is a bit odd and mismatched with a heatpump that is only the bare minimum for our square footage and way over the top TRANE air handler (that all 3 technicians commented on how mismatched and overengineered the air handler is to the heatpump). I would rather not spend 3-7k to get a new heatpump air handler setup so I’m hoping there’s something simple I’m missing. Here’s the nest wiring setup ( https://imgur.com/a/09mkLIn )