Hi,
I'm having exactly the same issue. I pre-ordered the Growing Together Pack and when it came out, my PC automatically switched me from Origin to the EA app and I've had nothing but issues since.
I loaded The Sims 4 to check out the Growing Together Pack and it said it was installed on the EA app but in game it said I didn't own the content in buy mode and on the main menu it says "download to use".
I've tried uninstalling The Sims completely, doing an app recovery, clearing the cache, updating the app, reinstalling The Sims and repairing it and since doing this, I'm now having an issue with all of my other packs/add-ons. I was given the option to download them again which I did and the EA app says they're installed but in game on the main menu it says "restart to use" against all the packs except for Growing Together where it still says "download to use" and in build mode it says I don't own the content.
As a result of this, I currently only have access to the base game.
I won't list all the packs/add ons that are missing as there are too many but I own every single Sims 4 Pack, Stuff Pack and Kit so it's literally all of them.
Any help would be greatly appreciated as this is incredibly frustrating. I just want to enjoy the new pack along with all the others I had before. I've not been able to play with the new pack yet and it came out over a week ago now ☹️
Thanks in advance!