Just so you are aware. Any games that come with activation keys will only work when it comes brand new with an activation key.
I have never bought a used game with a functioning activation key. GameStop and EA are not liable for there not being an activation key. When doing in store credit for selling a used game to GameStop activation keys aren't even considered. Sadly there is no legal obligation for GameStop to sell used games with functioning activation keys, there is also no legal obligation for EA (or any other video game company) to issue a game keys for any of their used games purchased through a third party.
It's the frustrating and annoying way that both GameStop as well as the game company (EA in this case) to make more money by having you purchase a brand NEW copy of the game.
To get The Sims 4 brand new on PC you are better off purchasing a brand new version of the game from GameStop or directly from the EA website. For the Console you're better off just purchasing the game brand new or getting it from the Console game store.