Every now and again Steam will decide to Show a unknown error popup when starting a game:

"Steam- Failed to start game (unknown error)"

The only way I can fix this issue is to restart Steam. This is troublesome because I am always in a voice chat when this occurs. I have no other programs running when this happens.

What could be the cause of this?

  • 2
    Does it only happen when you are in voice chat then?
    – Brok3n
    Jan 25, 2015 at 3:31
  • 2
    To give a more accurate answer, you might need to give more specifications such as your computer's specs, but... I gave you some options to explore on the answer below :)
    – Kim Minseo
    Jan 25, 2015 at 10:39
  • 1
    @Brok3n it can happen whenever, but that is when it is most cumbersome.
    – DavWhodums
    Jan 25, 2015 at 19:42

1 Answer 1


If you are using a 32-bit operating system, it is strongly possible that the executable file is developed for the purpose on running on 64-bit, not 32-bit thus causing the error. Or it might also be possible that your computer can't recognise the .exe file as a 32-bit file, thus failing to start the game.

Another possiblity is that your DirectX may be outdated, thus preventing the .exe file from running. If this is the case, you can find out how to download the latest DirectX (DirectX 11) here: http://support2.microsoft.com/kb/179113

In addition, a lot of cases might be that your antivirus firewall is blocking the game from running. If you have any antivirus program on, you might want to turn them off.

Source: http://steamcommunity.com/app/299720/discussions/0/35221584612613774/?insideModal=1#p2

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