Jus try to get all the original mw2 files, or re-install the game, or use yer backup, (backup again!) and re-apply the patch. Make shure yer iw4mp.cfg has auto update enable to 1. Also wrong section. Shud b in the help section
EDIT: i fogot. If u have 0 players online, its most likey becuz u applied the patch wrong.