I have a magic chef that has microwave grill conventional oven every thing works except microwave don't heat

It sounds like the magnetron may have either failed or is not being supplied with the extremely high voltage required to run it.
Make sure the !!!!capacitor is discharged!!!!! before attempting any sort of repair.
Check the door interlock switches first then the high voltage diode with either an AVO model 8 on high resistance range for short circuit, the capacitor can fail and go short circuit, the feed fuse on the primary of the high voltage transformer and then finally, the magnetron is best checked by substitution.
Hope that helps.