Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
You have stated that the LED Headlights no longer illuminate when Locking and Unlocking the Vehicle. Are these the same Lamp Units that are used for the Dipped Beam Lighting on the vehicle? If so then obviously the Lamps themselves work when using the Headlamp Switch. Because of this I would be looking at one of the following:
If the Lamps are separate to the Headlamps and maybe mounted in the Bumper Area then potentially it could be a corrpded connector to the Lamp Units where the Bumper Harness joins the Engine Bay Harness. It would be doubtful that two Lamp Units would have expired together hence checking the wiring first unless one had failed and you hadn't noticed it and the the other failed a while later in which case it may be the lamp units that are faulty.
You haven't provided any vehicle details so this is just general advice applicable to a range of vehicle. If you have a Registration Number I can check to see if there are any wiring diagrams available to provide any further information.