Re: [CURRENT ISSUE] Sims 4 DLC shows as installed, won't load in-game
@taytastic23 You can only use your Steam-owned packs in a Steam install. The reverse is not true: your EA-owned packs will install into the Steam base game. So the fix here is to uninstall the EA App version, install Sims 4 through Steam, then sign into the EA App and download the packs (but not the base game) you own there.
Anything in Program Files\EA Games\The Sims 4\The Sims 4, with that second Sims 4 folder, isn't going to be read by the game, but that's a separate issue that becomes irrelevant once you switch to a Steam install.