There may be various reasons why the Midea microwave oven does not heat up:

1. The second door interlock switch is broken, which prevents the microwave oven from starting or heating up. Repairing or replacing the interlock switch is necessary.

2. The high voltage transformer is damaged and the microwave oven is not able to produce microwaves and therefore not able to heat food. Replacement of the high voltage transformer is necessary.

3. The microwave tube is damaged and the microwave oven is unable to produce microwaves and therefore unable to heat food. Replacing the microwave tube usually solves the problem.

4. Damaged high-voltage capacitors or high-voltage diodes, the microwave oven may not work properly, resulting in the inability to heat food. Replacing these damaged components can usually fix the problem.

5. A broken door hook prevents the microwave from starting or heating. Replacing the door hook can fix the problem.

6. The cooling fan does not turn, and the microwave may stop working due to overheating. Fixing or replacing the cooling fan is necessary.

7. The primary coil of the transformer is disconnected, which prevents the microwave oven from heating food. Repairing or replacing the transformer can solve this problem.

Besides the reasons listed above, there are some other factors that may cause the microwave oven in Midea not to heat up, such as malfunctioning of the control panel, tripping of the thermal protector, and so on. For these issues, a professional may be required to overhaul and repair.