You will need to log into Facebook itself from your PC and remove GI Joe: War on Cobra from your Facebook's list of games in the My Games section. Connecting Facebook doesn't use the Facebook app, it instead uses the Safari Facebook login, which doesn't always match what the app is using, and can cause some headaches. The best way to fix this is:
  • Remove G.I. Joe: War on Cobra from your Facebook My Games section.
  • On your device, sign out of Facebook in Safari.
If you would like to link it to Facebook again
  • Close previous steps and launch the app again.
  • Now try to link your Facebook profile again from the game.