My friend just went through tons of hassle to get the trunk to open because he disconnected the battery and shut the trunk. We just found out from Meredes Roadside Assistance that the truck is to put in the key, turn all the way to left, push the button in... AND PUSH THE TRUNK DOWN to open it up.
Older mercedes don't need to do this... when we push the button, it pops open the trunk. The newer MB has the electric button to replease the trunk for us.
There you go... if you can remember it... LOL.