@Lanceleve1234 I think there might be a miscommunication here, but I'm not sure whether it's on your end or mine. When you own packs through both the EA App and Steam, each game launcher will only allow you to download the packs you own there. So you can only download the one pack you bought in Steam through Steam, not through the EA App. The App will say "manage on Steam" for that pack. It should NOT say "manage on Steam" for any packs you own through the App.
Steam will only show the one pack you bought there as owned. It will say you haven't purchased all the packs you own through the EA App. This is normal and fine, and it's why I said download the base game through Steam, then any packs you bought from EA through the EA App.
If this isn't possible, if EA is telling you to "manage through Steam" for the same pack that Steam says you have to buy, please make sure you're signed into the correct Steam and EA accounts. Open a private browser window, go to any EA site (this one is fine), and login with your Steam credentials. You should land in the EA App account you're using. If you land in a different account, or if you get an error instead, let me know.
Otherwise, please post screenshots of Steam saying you don't own a certain pack and the EA App telling you to manage that same pack through Steam.