Take a look at the diagram. Just to make sure we understand what is happening. You are putting the belt on as shown and tightening the adjusting bolt to add the tension and then tightening the lock nut to hold it in place? If so and it is not moving, it sounds like the bolt may be stripped and not actually moving the pulley.
If you can get a video of what is happening that may help us figure this out but if it is not moving when turning it then you will most likely need to replace it.
Sunday, October 18th, 2020 AT 9:18 AM