Why does this happen？The reasons are as follows
1. the driving procedure is wrong
2. the main motor circuit failure, such as fuse blown
3. the interlock device associated with the main motor is not turned on
How to solve this problem?
1. Re-drive according to the correct driving procedure.
2. Check the main motor circuit, especially if the fuse is damaged.
3. Check the working status of the lubricating oil pump, main motor
cooling system and other interlocks system of the main motor.