1.  Just restart your PC and try to start the game again.

If that doesn’t work:
2. Please verify the integrity of the game cache with Steam:
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335

If that also doesn’t work:
3. Make sure your firewall/antivirus software is put into gaming mode or has an exception for the game so it doesn’t block the game’s connection to the steam client.

Posted in: Errors