Hi Amanda,
Here's some information that you might find useful.
1.) Serial Code Already Used?
You only need to activate the game once. After that it's registered to the account you've activated your game on. That cannot be changed.
To reinstall your game, follow these steps:
If you don't have the Origin client installed on your computer yet, you can download it here:
http://origin.com/downloadLog in to your account with your email address and password. Make sure it's the same account used to purchase/activate the game. Or else it won't work. Find the game in the MyGames tab to download/install.
2.) I Can't Find/Manage Sims 4 and It's Game Content
In the Origin client, go to the My Games Library tab to find your installed games, such as Sims 4. Either right-click select Show Game Details or click the game icon to view game details/manage game content.
Click on the word Filter up in the right corner and select hidden games to find games that might be hidden.
2a.) If the game is no longer shows up on your Origin client, please try the following:
Restart Origin
Log out and back in. Use the email address instead of the username. Make sure to use the one you used to register the game in the first place.
Reinstall Origin
Restart your router/modem
3.) How to contact a Game Advisor using the new EA Help page.
http://answers.ea.com/t5/Answer-HQ/How-to-contact-a-Game-Advisor-using-the-new-EA-Help-page/td-p/2161281Hope this helps,
MrsFlynn