I run in Windows. I'm currently running the 'Legacy' edition of Sims4
@KpoppyJ I've moved your thread to the Sims 4 PC tech forum.
One common cause of this error is Windows 10's Controlled Folder Access blocking Sims 4. You can set exceptions for both TS4.exe and Origin.exe:
https://crinrict.com/blog/2019/03/windows-10-defender-controlled-folder-access.html
If you have a third-party antivirus/firewall, it could also block the game. You can test by disabling it temporarily, and if that's the issue, just set the same exceptions.
If this doesn't help, you can try the other steps listed here:
https://sims4.crinrict.com/eng/2014/09/unable-to-start-initialization-error-at-startup/
@KpoppyJ If you open Controlled Folder Access as described, what do you see? You can post a screenshot if you want.
It would also be good to see a dxdiag on this computer. You can attach the results to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
