What year is the car?
How has the actuator been confirmed as working?
With pre-'92 cars: actuator functionality depends on how it is installed. The mounting holes in the door frame are oblong. Positioning the actuator too close to the door jamb will result in a door that locks and can't be unlocked (fun). If it's too far away from the jamb (closer to the window regulator),the actuator will prevent the door from locking, and probably the rest of the car.
I would start by pulling the door panel, removing the actuator and checking the manual operation of the locking mechanism. Once that element is confirmed, align and install the actuator. Before reinstalling the door panel, assure that the central locking is working as it should.
best, whit