Seat belt is locked it wont go back in or out

try changing the seat belts

Seat belts are not fixed they are only replaced.

Check to be sure it is the right belt and latch combination.
I believe you have 3 seat belts in the rear. The latch for the two side ( door) belts is not the same as the one in the middle.
VERY often, one of the latches will fall down in between the seat rest and the back rest of the seat, often from dis-use.
This happens on all cars.
You should have 3 latches on short straps in the middle of the rear seat.
Be blessed.

The problem:
The set belt stop has been lost so the seat belt retracts too far when the seat is laid flat. When laid flat the release mechanism lock as it should when not level. So the seat cannot be raised up as the belt is too tight and locked.
The Solution:
1) Push the two little clips to release and remove the headrests.
Pull the grey lever on the right of the seat base, lift seat base up and forward toward the front seat..
2) See two red capped leversat the back of the two seat hinges and lever them to the upward position, this releases the seat.
Rock the very heavy seat unit upwards and lift complete unit upwards.
3) Take it out of the car and turn 180% so that the back of the seat and base are in the upward position and the seat belt will pull out as it should
4) Replace the missing belt locking stop (I used a tie pin permanently fixed using super glue).
5) Fold seat back down and test then either re-fit seat unit or leave out to decrease fuel consumption..

You can try to pull on the belt with the plastic trim piece removed the take a flat tipped screwdriver the release the arm or bar holding the belt in the lock position. Most of these have a spring on them. That spring can fall out. Or sometimes the bar or lock arm may be jammed and needs to be pried loose then lubricated to prevent this from repeating in the future.

Hi, We are having the same problem with our son's car. Were you able to come up with a solution?

middle seat belt shouldn't have anything to do with it. The seat locks down for stowage in the rear cargo area. you can pull the release handle on the back of the seat to release it back into the up position.

Push and roll the seat belts all the way back into the container and then slowly pull them out.
If you do it fast they will lock.
Vitally

I assume you've already worked the seat belt end back and forth with force. Did the belt move at all? Did you remove the rear seat bottom cusion from the car? That will give you additional leverage on the belt.
If the belt twisted the last time it was used and then rolled up, you need to go to the dealer or an upholstery shop for help.

get your dealer to replace the seat belt, depending on age, should be under warranty. Belt is defective. I have a g 2003 vue, and my dealer replaced the belt for no charge.