There could be a few reasons why your Call of Duty multiplayer isn't working. The most common issue is that you may not have the latest update installed. Make sure you're up-to-date by going to the App Store and downloading the latest update. If that doesn't work, there could be a problem with your internet connection. Make sure you're connected to the internet and try again. If that still doesn't work, it might be a problem with your console itself.