I downloaded the free sims 4 and it won't let me purchase the expansion packs

@Mooganfreeman94

If you have already downloaded free The Sims4 you don't need to buy it again. All that you need is to check if this game is in your Origin library.
If it is then it is Origin fault - Origin doesn't read it correctly.
Clear the Origin cache
https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/