Everything works except the food does not heat up. Any recommendations?

It is more than likely the magnetron. It could be the high voltage diode but that usually make a loud pop when it goes out. the capacitor usually shorts this will blow the power fuse. Magnetrons are not hard to change just fairly expensive.

This could be a diode or a capacitor. It is not expensive to fix if you have the time and patience. If you don't then you should take it into someplace to have it repaired.