is it cable operated or does it use a solinoid?

it sounds as if there is asomething just stuk somewhere that's not allowing the door to lock as it's stuck in the open position

have you tried closing the lock with a screwdrivr or the like and seein what part of the door is sticking when you lock it?
remove the panel and you can test individual items to eliminate them from the equation but the first step would be to see if the motor locks/unlocks when it's wired up but not connected