@balibali24 I don't really know how purchases work through Epic, but it's possible you were paying Epic for the packs and simply using the EA App interface. Does your content show as owned in your Epic game library?
Does the Sims 4 base game show as owned in the EA App? If so, can you click Manage > Manage add-ons, and do any of your add-ons show there? If so, even if you could buy them elsewhere, you should be able to download the packs into your Steam install. Make sure you have only the one copy of Sims 4 installed, and then click Download for each of the packs, but do NOT download a second copy of the base game.
If you don't see your content in the EA App, please make sure your EA and Epic accounts are currently linked correctly. Try to sign into any EA site (this one is fine) using your Epic credentials. If you land in the correct EA account, they're linked; if anything else happens, let me know.
