A support case was created for you and you should be contacted shortly by a Customer Support Representative, if you haven't been already. You can view and update your case at the Activision Support website. After logging in, go to "My Support" then "My Cases".
What console are you playing on? If this is for PS3, try the following steps.
Go to your game data utility folder then from there, look for Black Ops 2 data with the "-install" at the end then delete it then reboot your console. Now, try the game again then check if it would now work.