Will it not close FLUSH, or not latch... if it won't close flush with the rest of the body, then the latch may have been manually pushed in, on the inside edge of the door (I'm sure you've done this to your parents door, as a kid...)
If it goes flush, but won't latch, then check the latch for it to be binding, etc... Open the passenger door and look at the latch, while opening the door from the inside, or outside... see if the latch moves freely, etc. Try a little WD-40 on the mechanism, see if it can be freed up.
Ray
