s500 w220 electronic ignition lock
 

mercedes dealer changed my eis because it stopped working.i got home from the dealer,next morning same thing key wont turn in ignition,and the airbag lamp is on softclose not working and i cant lock car...so much for mercedes workshop :(

return ure merc and complaint back bro.... that aint right doing the wrong thing and having the same problem.... gosh i know how u feel *dissapointed*

Sounds like something didn't take.
Did you try a new key before they replaced the unit?