Rear middle seat belt won't pull out

I just noticed that when I try to extend the middle seatbelt, it won't extend at all. The only thing that changed in the past few days is put rear seat covers on. Before that, I've never had a reason to use those the middle seatbelt so I can't say whether it worked before I put the seat covers.

Except in this situation, the rear middle seatbelt is already retracted all the way.

Can anyone think of something simple I should try before taking it to the dealer? It almost feels like when you are installing a child seat and extend the seatbelt all the way and let it retract a little bit and then it won't extend until you retract it all the way.

i guess I will just bring it to the dealer.

Once I folded the seatback forward, the seatbelt started working again. I guess I will keep an eye on it.