Re: It says the code has been redeemed already
@marianna_stp Please clear Origin's cache:
https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/
Restart your computer, then login to Origin. Open your Origin game library, click on the Sims 4 icon, select More > Expansion Packs, scroll down to Island Living, and see what the orange button says. If it says Download, go ahead and download the pack. If it says Details or Play, the pack is already installed.
If it says Buy Now, you'll need to contact EA customer support to ask for help. It's possible that something went wrong with the purchase, or with your game library.