Re: My Sims 4 expansion packs aren't showing up in Steam.
@JadaCamille You need to install Sims 4 through Steam, then download your packs (but not a second copy of the base game) through the EA App. The option should be under Sims 4 > Manage > Manage add-ons. The packs should install into the folder for the Steam-installed base game, and everything should load from there.
If your packs show as installed in the EA App but don't load in-game, you probably have this issue:
Please see the first post and accepted solution on page one.
Origin doesn't work in Windows anymore, which is why you get an error when trying to install it.