The cfs 3 server has been down for a month now. Microsoft say's they're working on the problem but we all suspect that they are no longer supporting the game. My best recollection is that the game was released about  5 years ago so that would put it at the end of their support. Sorry

You can start by going to sim-outhouse and looking in the cfs 3 forum's. Lot's of player's are now posting privately hosted game's on there. I'm sure that someone would be delighted to have you join one of their game's. I'm in the same situation as you, only purchased cfs3 1 month before server went down and I'm anxiosly awaiting the outcome of all this. Hope this help's you out my friend.