S550 Mercedes You press the remote to open but the lights come on but the door will not unlock you use the mechanical key to open the door you cannot lock the car with the remote?

The door lock module/solenoid in the driver's door is bad. You will need to remove the door panel to get to it. Make sure you have a fresh battery in your keyfob just to make sure it isn't sending a strong enough signal to the locking mechanism but enough to trigger the interior light.