Not working

Hello. What to do if the client does not work? When I downloaded it for the first time, everything worked. I played a lot, but it’s a pity to somehow lose my account. I recently downloaded the game, installed a new client, and the game did not start. I deleted the CallofDuty4MW folder, it did not help, I reinstalled the game and the client, nothing either. Once I started the game, but there is no client there, just the Internet, favorites and local network, nothing else. I don’t know what to do, I’ve tried everything and nothing. I want to play again.