My daughter ran the microwave empty and now it doesn't heat up! It's a Kenmore over the oven type. Help!!

The magnatron is gone. If you put a cup of water in the microwave and try and heat that up and it does not heat up then the magnatron element is gone. Would suggest you buy a new oven. Running the oven empty would not harm it. Have owned micros since 1974.

If you posted this right after it happened, allow the microwave to cool. There is a thermal sensor on the magatron which should automatically reset.