Can't activate The Sims 3 even though I purchased the game!

My mom bought me a copy of the game on Amazon. An actual copy, not a digital copy. And I'm pretty sure it wasn't used. 

But today when I tried to install it I couldn't activate it. 

First I tried activating it from the actual origins installer or whatever it is. And a red thing came up saying, "We're sorry, this code cannot be redeemed here" and then gave me the link to register the game on the website. 

But then I put in the code and it said it was invalid! 

And I don't know how that can be. I tried entering the code several times, uppercase, lowercase. I double checked I was typing it right. And every time it was invalid.  I've probably checked the packaging 50 times to see if I'm missing something. 

I'm pretty angry. My only birthday present and I can't even use it.