The three locking hooks are all connected to the same rod. When one hook moves, all three move.
the hook latches of the FUHR sliding door lock automatically engage when the door is closed. Two srings are built into the lock, which constantly exert an upward force on the hook. Hence, the natural position for this lock is locked position, rather than unlocked.
When the door handle is cocked in the unlocked position (when you unlock the door), the springs are compressed. The springs remain compressed until the trigger on the lock make contact with the door jamb; the pressure on the springs is released and the hooks move upward into the locked position.
The Problem With Your Lock Problem:
If your door won't open but your handle still turns, the root of the problem is probably likely that the hooks are stuck on the strike plate. The most likely reason this would happen is that the door panel is not square and level with the door frame. The hooks are put under pressure and are in a bind. So, even though the handle moves, the hooks are wedged, stuck, in the strike plate and the door cannot be opened.
How to Tackle the Problem:
Make sure that the key cylinder in the door is actually unlocked, so that you don't break the cylinder while trying to fix the issue--or do more work than you have to to fix it in the first place. If your handle moves, the key cylinder is not locked. If your door is locked, turn the thumbturn to unlock it. From the inside, if the door latches on the left side, the thumbturn must be turned clockwise to unlock the door. If the door latches on the right side, the thumbturn unlocks with a counter-clockwise turn.
With the help of another person, see if you can work the hooks out of the strike. While one person is turning and pulling the handle (as though opening the door), the other person should move the panel up and down and back and forth. See if the hooks can be wiggled out of their jamb.
If that doesn't work, remove a piece of the interior trim and expose the door frame from the inside of the house. This will allow you to see the hooks.
Using a flat blade (putty knife or pry bar), you should be able to get in between the panel and the jamb and move one of the hooks enough to pop the door open while pulling on the handle. Remember: all three hooks move together. If you move one hook, all three will move.
How to Keep the Problem From Happening Again:
The trick once you get the door open is to re-align the sliding panel and the door frame. There is most likely nothing wrong with your lock--over time, something has caused the panel and frame to get out of whack with each other. The first step is to check the rollers. These may need replacing, but at the very least, they could probably use adjusting. If one roller is higher than the other, then one side of the door is higher than the other, and the door panel won't be square with the frame.