look at the door frame were the upper and lower latch (bolts) from the door" go into the frame, as they are different from the KEY lock" when you push up the handel to lock the door , the bolts lock into the frame,, make sure that the black or white ect" strip of plastic in that part of the door frame has not moved up or down, blocking off some or all of the holes were the bolts go, if so use stickey tape to hold the strips in place ,, check this first,,
mick, January 2011