Sometimes the rear seat belt retractors get stuck and prevent the seat back from folding down. I've had it happen several times and had to go to the inside of the car and "jiggle" the seat belts a bit to release them.
My trick is to tuck the belt on the sides in the gap where the backrest parts away from the rest of the rear "deck". Takes a few sections and avoids the annoying process of running back to the rear passenger area.Sometimes the rear seat belt retractors get stuck and prevent the seat back from folding down. I've had it happen several times and had to go to the inside of the car and "jiggle" the seat belts a bit to release them.