abistasiasims You shouldn't need to login to the launcher to install your Store content. Are you being asked to do so? In that case, do you own multiple copies of Sims 3? For example, I've registered a disc copy and one from Steam.
Please also test in a new admin Windows account. Make it local, as in, don't link it to your Microsoft account or any email address. You'll be able to test whatever you want without reinstalling anything.
The "serious error" is usually OneDrive-related. Please see the first post of this thread if you run into it again going forward:
[Current Issue] Sims 3 "serious error" when loading save | EA Forums - 8322938
Playing the game in a local admin account fixed everything. Does this mean I will have to log into a different windows account when I want to play TS3 now?
As for your first question, when I am on the store's website and hit download (using my main Windows account), it opens the launcher on the login popup and if I exit out my item isn't there in my launcher for me to install. And my only copy of the Sims 3 is from a disc.
