Another RVcomfort.HP Thermostat Issue

[JaycoAl]

Last Sunday I tried to run the furnace but the thermostat read "00" and reverted back to the room temperature. Raised the temp to 80 to get the furnace to come on and the same "00" appeared on the readout and back to room temperature. Left it alone and let the AC do its job while I researched. Tried it again tonight with all the recommendations done after researching and the same appeared, "00" but this time the fuse in the thermostat blew. The T-stat manual says to check for a short in the furnace before replacing fuse. Wondering if anyone has had this blown fuse issue and where the short was actually found. Coach is plugged in with 13.10V at the fuse holder.