Serial Number not registering online

I bought the Sims 3 Generations online from Amazon.com. They supplied a keygen and the download was successful. I also have my online community account where if you enter the serial number it will register your game with your online account. When I go to input the serial number I get an error message saying the number is invalid! However I bought the game legally and have the creditials to prove so. 

What to do?