Hello, this method did not help me.
- Uninstall the game.
- Make a backup of Arma 3 folder in Documents.
- Delete both Arma 3 folders in Documents and Steam:
\Users\*YOUR USERNAME*\Documents\Arma 3
\Program Files (x86)\Steam\SteamApps\common\Arma 3
- Reboot your PC.
- Run Steam as Admin, download the game.
- Try to run Arma 3 (without mods).
2 weeks struggling with this error, please help, I'm losing hope again to play in arma :(