McKenzie4291 You may simply have Windows Defender, which doesn't usually cause problems with Sims 4. But Controlled Folder Access (a feature of Defender) can block Sims 4, so please change its settings or disable it—just CFA, not Defender overall. Here's how:
https://crinrict.com/blog/2019/03/windows-10-defender-controlled-folder-access.html
If you do have a third-party antivirus, you should see that in the same location in Windows Settings.
If this doesn't help, is OneDrive running on this computer? That could also trigger this error. Look for a cloud icon in the lower-right corner of the screen, and if you don't see it, open the Tray (^ icon) and look there too. Right-click the cloud icon and select Pause syncing, choose whatever time frame you want, and try again to play Sims 4.