Initilization Error at startup?

@Simologist  Just checking, but are you still running Origin and Sims 4 as an admin?  Do you have an antivirus currently running, and if so, have you tried disabling it?  Even if you did before, it's worth trying again now, since both the game and some antivirus programs have updated since you first posted.

If none of that helps, try uninstalling and reinstalling .NET Framework 3.5.  Hit Windows key-R and enter "appwiz.cpl" without quotes, then in the File Explorer window that appears, click "Turn Windows features on or off."  You'll see this:

Click the box next to .NET 3.5, shown at the top in blue, and let it uninstall.  Then restart your computer and repeat the above, except that clicking the box will reinstall the framework.  Restart again before trying to play.