Corrupted cache files can cause startup errors.
If none of the above steps work, the game installation might be deeply corrupted. Uninstall The Sims 4.
I encountered a persistent startup error in The Sims 4: "Unable to start. There was an error processing the startup configuration script (exclusive)." The message appears immediately when launching the game and prevents any play. After trying the usual fixes (repairing game files, running as administrator, disabling mods, and updating drivers), the error still occurred intermittently—sometimes the game launches after multiple attempts, other times it won't start at all. Corrupted cache files can cause startup errors
The most common cause of the "Exclusive" error is a localthumbcache.package file that is corrupted or a GameVersion.txt file that the game forgot to release.
Turn off or add TS4_x64.exe as an allowed app. I encountered a persistent startup error in The
these files/folders (don’t worry, saves and mods won’t be touched unless you delete them):
Corrupted files often cause configuration errors. A repair will check all game files and replace any that are damaged. Open the EA App and go to My Collection . Click the three dots ( ... ) on The Sims 4 icon. Select Repair . Steam: Go to your Library. Right-click on The Sims 4 . The most common cause of the "Exclusive" error
Microsoft OneDrive is a frequent culprit. If it is syncing your Documents folder, it locks files milliseconds before Sims 4 tries to access them.
How to Fix The Sims 4 "Unable to Start: There Was an Error Processing the Startup Configuration Script"