Dear Mercedes forum users,

My brand new key (ordered from Mercedes Benz Canada) works initially, but then the car won't start (or turn-over) with the new or old key. When I try again in 24 hours - car starts with the old key - try the new key again, starts, then back to the same issue of not starting with the new or old key. This has been repeated a few times (insanity on my part I guess). I've now avoided the new key for over a year - but I will eventually have no choice but resolve this issue as only one old key remains.

Any suggestions?
With thanks,
F.Y.I. - I have also posted this Quere on the E320 area.