Amazon thermostat not engaging fan for heat.

Hello! New homeowner here and I’m having a slight issue with my Amazon Thermostat. It mostly works, the only thing that doesn’t is the heat does not trigger the fan in the air handler. The fan in the air handler works with AC however. It also works when independently controlled.

Boiler pic, wires to thermostat are in the lower right. Air handler pic, the bundle of wires in the white sleeve go to the thermostat and the brown sleeve bundle go to the outside compressor. I added the black wire wrapped around the white sleeve to the common terminal to power the thermostat. I did this after I took the pic.

Could it be something with the Y/Y2 and Y1 wires? Also, on the old thermostat RC and RH were reversed and jumped. The common wire wouldn’t power the thermostat until I connected them properly to complete the circuit with the common wire on the air handler.

Thank you in advance!