Rich, there are a lot of different variations since there were a lot of different manufacturers but here are 2 things to check. First, just lift the door straight up and see if you can then move the bottom out. If this does not work, look for screw heads on the stile of the door. If you find these, they are used to push down on the roller frame that is hidden in the stile. Turn the screw counterclockwise several full turns and see if you get more play when you then lift the door up door up. If this seems to work, keep unscrewing until you get enough clearance to swing it free. If this doesn't work, look for screws in other locations and they may give you a hint. If this does not work, have someone else lift the door while you try to slide a knife blade along under the stile until you find the roller location. Use the knife to push the roller up while you slide that end of the door off the track, then do the same on the other end. If that does not work, find the oldest hardware store or oldest glass and screen repair shop in your immediate area and ask the oldest employee.
Hope there is an answer in there for you somewhere.