Truck will not open automatically only opens with the mechanical key

I assume you meant trunk? This sounds like valet mode. Insert the key in the trunk and turn it 90 degrees. Pull it back out and try the remote. If that doesn't work, point the key at the IR receiver (little black rectangle on the driver door handle) and hold the trunk button for 15 seconds, then, within one minute, put the key in the ignition and turn it to "ON" without starting the engine. Wait a few moments, exit the vehicle, and try it again. If these don't work for you, check the link below for some hands-on help. http://repairpal.com/mercedes-benz-within-10-miles-of-asheville-north-carolina-28805