Hello,I will be glad to try and assist you with this,Welcome to Just Answer.
If the seat belt was twisted when it restracted the last time it worked then this will cause the belt to jam up and cause this condition.
The set belt has a lock on it to lock whenever extrme force is present especially during a collision,if this lock fails it can cause thie problem,it can either fail to where it wont lock and hold the set belt from retracting ot it can gfail and stay locked and keep the seat belt from pulling out.In this case which is most likely what has failed on your vehicle here the seat belt has to be replaced.
Unfortunately you cannot tamper with the seat belt to try and fix this concern for safety reasons,the entire seatbelt has to be replaced to fix this concern.The best place to have this done is at a dealer,but any other shop should be able to do this repair.The part if wanted new will have to be purchased through a dealer but a used may be obtained through a junk yard.
Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
PETE, I WILL ACCEPT YOUR ANSWER BUT ONE MORE QUESTION. APPROX. HOW MUCH FOR THE REPAIR ASSUMING THAT'S THE PROBLEM?
My estimate guide doesnt give me an exact price most likely being due to the year of the vehicle but the seat will have to be removed and taken apart in order to replace this so it can coist up to 4 hours labor to do this removla,dissasemble and replacement.
The part can cost up to $300 depending on what type of belt it is and whether or not it has the ETR(emergency retracting device).
I hope this info helped,Let me know if you need anything else,Thanks Pete!