The Mégane II Owners' Club

How do fellas, just bought a new stereo... Managed to get the original one out with ease, however tried plugging the wires in to the new un... However....no lighty... No likey! Any help will be much appreciated.
Cheers fellas.

Need to give us some more info and I'm sure I can help as just fitted a doiuble dinn one in my GT over the weekend and worked first time.

What happens (if anything) and is it an original or modified harness you are plugging in?