It looks like the piece on the left should lock in
I took the rear seat out few weeks ago and when. I put it back on it installed and amp on the back on the seat. I haven't tried closing it because I wasn't finished with the install completely. Today I went to clos3 it and it won't close. I took the amp off and the screws . I was able to manually close the latch with a screw driver and a some force. I opened it with the rope.

 

Never mind it's got i ty again