Is anything else not working ? The wall controller can’t tell the ac to turn on if it’s not getting 12v to function… so I’d be looking at the other fuses or and inline fuse from the battery as low hanging fruit.
I have the same thermostat. There is a little barrel fuse in it which you can see if you take off the cover. Mine was blown in the winter. Although I think with my blown thermostat fuse the fan would still turn on when set to FAN and ON, just nothing worked when set to HEAT.
Not sure if it’s your issue but anyway it’s something to check.
