@puppieandkittie, sounds like you might need to reset Origin. Don't worry if the code was redeemed, the game should show up under the Expansion Packs once you reset Origin. If resetting Origin doesn't work and you truly cannot redeem the code, you will need to contact EA Customer Support, provide proof that you purchased the game (receipt, email) and they will help you further.
Here is the link with instructions on how to reset Origin.
https://answers.ea.com/t5/The-Sims-Mac/READ-FIRST-Origin-Troubleshooting-and-Information/m-p/5371659#M3386
