The lack of heat in the microwave oven may be caused by many reasons, such as a broken fuse, a broken turntable mechanism, a broken microwave tube or motor, and so on. If you find that the microwave oven is not heating, you can try the following methods:

1. Check whether the power connection is normal. Make sure that the power cord plug is firmly inserted into the socket and that the socket is powered on.

2. Check whether the fuse or fuse inside the microwave oven is damaged. If the fuse is blown, please turn off the power supply, replace the fuse or repair the microwave oven.

3. Check whether the turntable mechanism inside the microwave oven is normal. If the turntable is stuck or damaged, you can try to clean the turntable mechanism or replace the damaged parts.

4. Check whether the microwave tube inside the microwave oven is damaged. If the microwave tube is broken, it usually needs to be replaced. If you don't know how to replace the microwave tube, you'd better seek the help of professional maintenance personnel.

In short, when the microwave oven is not heated, first check whether the power connection is normal, and then check whether the turntable mechanism, microwave tube and other components are normal one by one. To solve the problem as soon as possible, to avoid the problem becoming more serious, which may bring danger.