How do I fix the seat belt ribbon?

If its not pulling in at all I would think it needs to be replaced. The mechanism is a complex little part that can even have a small charge that fires with the air bag to tighten the belt a little.

When you pull the belt all they way out dose it make the typical seat belt noise? Then its just all out sitting there with zero tension?

I had a belt that would retract slow or only 90% of the way; I washed the belt in hot water to make it more flexible, that helped a lot.