Door lock mechanism on 2002 Mercedes-Benz C320

Driver side door lock mechanism does not go down/lock makes rattling noise. I tried using the key, the lock icon on dashboard. The other 3 doors lock and the alarm is activated but the door doesn't lock. Tried replacing the power latch control mechanism. Is there a reset button somewhere or something else that could be the problem?

Asked by for the 2002 Mercedes-Benz C320
Did you try a new door lock assembly? These are notorious for failing.
BRETB - thanks yes I replaced entire door lock assembly unit and it is working fine now.