my dad S class, he said that when he put in the key, nothing works or turns on. also you cant lock it or unlock it. mercedes road side came to check the battery and said it was fine. we didnt have time for them to stay long enough to figure out the problem

does anybody have an idea what the problem could be?

 

They came to fix it, but you let them go??

Sounds like a bad ground - or other electrical issue. If you can't jump it (measure the battery voltage first), have it trailered into the dealer and let them take care of it.....

Hopefully, you're still under warranty.