The lock cylinder pushes or pulls directly on the lock mechanism for that door.

Off the lock mechanism is a switch for the pump controls.

When you lock the door, you directly lock that door with the key and send a signal to the pump that applies vacuum or pressure to the actuators in the other doors. Sorry can't remember whether vacuum or pressure is lock or unlock at the moment.

So if turning the key in the lock does absolutely nothing then the cylinder is not hooked to the mechanism.

If you push the "golf tee" down with all the doors shut do the doors all lock? And if you pull up on the "golf tee" do the doors all unlock? If this is true then the lock system is working properly, you are just missing the connection to the lock mechanism from the lock cylinder.

If you remove the door card you should be able to see what is missing inside the door.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech