Dual fuel hvac on generator

Yes I waited until the last minute……….

Last week before the winter storm, I installed 30 amp transfer switch to hook up a 20 amp generator (free) using an adapter.

Everything works but the heater.

I’m guessing is because running the heat pump heater draws too many amps to start up and it’s not wired to be able to start just the aux heater.

Thoughts?

Thoughts on how to get it to start the aux heater if I’m right?

Thanks in advance.