Can't download Sims 3 dragon valley

I have been trying to download the dragon valley since i purschased the disk from gamestop. When i put the disk in it does the folowing:

asks me what language: i put english.. then it proceeds to where it wants to install but it imediately says its installed after i tell it too. then it takes me to the sims launcher to play the game where it pops up with a window to enter my 16 digit key code.. I do that and it has been saying invalid when my boyfriend and i both have done it for 2 days now.. I was really excited to play this game but I dont get why it won't work.. How do i download this world ?? I have been googling everything to do!!!!!!!!!!!!!! please help