If you are still experiencing this issue, here are some tips you may want to try.
You can always check online services status Call of Duty: Black Ops 2 Status
If online services are fully operational and you are still unable to connect, you may want to try the following.
- Reboot your router.
- Restart your system.
- Check the NAT type. Is it Open, Moderate or Strict?
- Establish a static IP address and port forward.
Here are the port numbers you will need:
Xbox 360: Activision Support
Should you have any questions on how to port forward, please contact your ISP or the router manufacturer.