The 2 most common part(s) or condition(s) which cause the symptom Microwave not working are listed below starting with the most likely. Check or test each item and watch any available videos.
RepairClinic Item # 1325821
Every microwave oven has a line fuse. This fuse is designed to blow if too much current is drawn through the microwave circuitry. The fuse can be replaced, but the underlying issue should still be investigated and resolved. Otherwise the new fuse will blow also.
RepairClinic Item # 1363720
If the microwave is not working the main control board may be defective. This is not common. When a microwave stops working the problem is usually the line fuse or within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.