I'm going to take a guess here and suggest a hair drier aimed at the latch mechanism. I had this happen one time many years ago with my Fiero GT and the problem was a frozen latch mechanism.
So I thought it wasn't frozen, but I took some hot water to it (I know... terrible idea but I just moved and didn't have anything else here) it latched and I went to the store and got some WD40. works like a champ now