Hello,

I am not able to play multiplayer mode of crysis 2.. i played some days ago but today i tried and i am not able to play.... It says invalid serial... What is happening ?

any help ?

This error is fairly straight forward to resolve, if you own a retail version of the game simply re-enter the serial key you were provided with. If you are 100% sure you have entered the correct key and you still have problems then you need to contact EA support.

The same applies to if you have lost your key, please get in contact with EA support, however if you entered it correctly the first time then this error should not have displayed in the first place.