Socket in the glove box

Open the glove box.
Lift up the cover of socket 1.
See also:
The windshield wipers are obstructed
Leaves or snow, for example, may be
obstructing the windshield wiper movement.
The wiper motor has been deactivated.
For safety reasons, you should
remove the SmartKey from the ignition lock.
...
Information for customers in California
Under California law you may be entitled to a replacement of your vehicle or
a refund of the purchase price or lease price, if after a reasonable number of repair
attempts Mercedes-Benz USA, LLC a ...
Vehicle remote opening
If you have unintentionally locked your vehicle (e.g. the SmartKey is still in
the vehicle) and a replacement SmartKey is not available, the vehicle can be opened
by a Mercedes-Benz Customer Assis ...
