I have a heat pump system just for the second floor of my house and rely on it more for the AC up there than for the heat since the gas heat from the first floor rises. I’ve had the freon lines freeze up during summer months due to a malfunction in the defrost cycle. The best solution to that is to leave the inside fan “on” at all time and not in “auto”. In addition to the possibility of a tripped breaker, there are cartridge fuses in the disconnect box which is usually inside the house near the “air handler” part of the system. If one of those is bad, I don’t think you’ll get the auxiliary heat either. A person can pull the disconnect (which will shut the system down). An unskilled person could take that whole thing to a LOCAL hardware store - not some home center chain - where those cartridge fuses can be tested and, if necessary, replaced appropriately. If they are bad, I’d buy some extras, too. A service manual would help, but maybe you can look this up online(?) for some “look at the pictures” kind of help. I don’t say it that way to be a wise guy. I say it that way because that’s what I’d need if I’d never done it before.