Some antivirus programs are known to block programs from running. This should remove any potentially corrupt or broken files and allow the game to run. Follow the above steps to set it to Run as Administrator.Navigate to your Steam install folder (Default: C:\Program Files (x86)\Steam).In some cases, running Steam itself in Administrator mode may resolve the issue: Once you have done this, restart Steam and try launching the game again. Check the Run this program as an administrator box.Locate the game executable (the application).Go to Properties then the Local Files tab.Right click the game in your Steam Library.To resolve this issue, please try the troubleshooting steps below: Run the game as Administrator The error 'Failed to start game (unknown error)' is a Steam error.