Just a couple of thoughts; the actuator is in the lock , the red lock tab is bowden cabled to the lock. Either the lock is seized up or the bowden cable to the red lock tab is seized up. The actuator may be fine and cannot overcome the friction of either the lock or cable. If it was just a weak actuator, the tab may still operate normally. Try pushing the tab and getting the unlock button pressed at the same time. We had a weak battery and the rear door wouldn't unlock, it would only go about half way. I lubed the cable and it allowed it to fully unlock, then a week later the battery wouldn't start the car. I was fully expecting to have to replace the lock also, but it turned out the battery was failing.