Left 4 Dead 2 achievements bug?

I recently linked my account to Playfire.

And I was playing co-op campaign and we finished the level in the mall with the car, but I didnt get any achivements....

The only thing I can suggest is: did you have any cheats turned on at any point during your playthrough? If so, you can't earn any achievements until you turn sv_cheats off and start a new session.

you don't always get the achievements, that doesn't mean that has something wrong with your account
some achievements take a little time and effort, and for example, you said that you finished dead center, but you need to survive in the end and get in the car. and as far as i know, you also need to survive every safehouse till end (that's how i got Price Chopper).

edit: i already played in a free holiday account and got the achievements, so it's not a bug or anything.