I have just set up the game and it goes on in singleplayer but I don't have received my multiplayer key.
Help me please.
Thanks.

Multiplayer key is the same as the Serial Key of the game.

Insert your serial key and you will be fine.

The serial key is the product licence code you need to install the game but with dashes every four digits. This is b.s. I've been screwing around for hours to find out they have to cofuse the issue by changing the names of the codes?