Open the back of the seat and check the cable that controls the lock for the seat.
Honda Pilot has the same problem, this link will help you:
http://www.piloteers.org/forums/14-problems/18995-middle-seat-latch-broken-wont-fold-down.html
Honda Pilot has the same problem, this link will help you:
http://www.piloteers.org/forums/14-problems/18995-middle-seat-latch-broken-wont-fold-down.html