How do I open stuck sliding door?
Try pushing the door closed as hard as you can and maybe this will take pressure off the latch mechanism allowing the door to be unlatched. I know of one case where someone took too much slack out of the the door by threading in the screw in the jamb too far. They then latched the door and it was stuck.

After you get the door to unlatch and get it open, adjust the latching to introduce a little slack in the latch. If it is a case of in-and-out alignment, you might have to bend or file one side of the hook, but I would suppose there is some sort of adjustment.