Welcome to just answer.
I am sorry to hear that your turntable is not spinning.
Can you check the following items:-
1. Do you hear the motor noises spinning
2. When was the last time the system Worked?
3. Have you ever replaced the belt?
Then I would think the motor has a damaged during storage and my suggestion would be to take the system apart to identify the problem and see if you can order parts and perform repairs.
I can also call you to discuss in details.