I should prolly also mention this happens when someone turns on the air conditioner without turning off the heater ( we have different thermostats. Any help would be appreciated.

Hello all. I have a Nordyne MGHA-070AAFC-01 and the safety switch won't lemme turn on the heat. It's cold lol This happened once before and we paid the guy to do 5 mins of work to turn back on and said it got to hot and the switch turned it off. Think anyone can help me out? What do I do? lol