single player works fine but evertime i go on multiplayer and i go to join a games it says key code in urs plz try again later and i changed the key code but it just says the same thing over and over
Sounds like someone has got access to your game key. Sounds to me like you have a pirate copy?... or did you buy it second hand?
If you are the legitimate owner who bought new... call the support line... with proof of ownership they can probably block your old key and issue you a new one.