There are two pins on the inside of the hood. One is the pin with the spring on it that engages with the latch mechanism and the other is the guide pin. I recently had to have my guide pin adjusted because I was breaking hood cables due to to much resistence on the pin.
I was told that if by chance your hood has been closed by dropping it you can bend or move that pin enough to cause it to stick.
That could be the problem.
Spiderman
P.S. - All of the posts and sockets should always be greased as well.