I'm having the same problem except on the passenger side, I've pulled the door panel on the working side, and operated the door unlock mechanisms (with the key on the outside of the car) I've noticed a distinct motor sound (the door actuator) on the working side, and on the non-working side this noise is absent. This leads me to believe that the actuator on the non-working side is not functioning. The problem now is how to get to the bad actuator with the door closed. I see two options, one is to sacrifice the door panel (cut it) to access the actuator, or (ugh) go to someone who deals with this kind of thing regularly. I would imagine the dealer is just going to cut the panel and charge me a fortune to replace it.