How to fix the ‘unknown function’ Call of Duty: Warzone fatal error

This is an ugly one.

Image via Activision

A new error code is hampering Call of Duty: Warzone players’ ability to log on and play the game at all.

The “unknown function” fatal error happens when players attempt to launch the game and directs them to Activision’s support page for Modern Warfare. Reddit and Twitter have been set ablaze with players reporting the error with little success on actually playing the game.

Unfortunately, it appears this issue has popped up as some kind of side effect after the June 3 update and will likely need a fix from the developers to squash it for good. On consoles, there’s not much you can do at this current point in time besides reporting the error to Activision and hoping for a fix.

On PC, however, there’s a few workarounds that have worked for some people by heading into the launcher and messing around. YouTube channel Tech Sites uploaded a video highlighting some of the potential fixes, which can be found below.

First, try the “scan and repair” option on If that doesn’t work, it might be time to get into the nitty gritty of the PC.

  • Open launcher
  • Select Call of Duty: Warzone
  • Click on ‘Options’
  • Click on ‘Game Settings’
  • Select the ‘Additional command line arguments’ box
  • Type -D3D11 into the box
  • Click ‘Done’
  • Launch Warzone

A second potential option:

  • Open ‘This PC’ or ‘My Computer’
  • Open ‘Documents’
  • Open Call of Duty: Modern Warfare
  • Delete the ‘Players’ folder
  • Open
  • Launch Warzone

With such a problematic error, Activision will likely be quick to fix it. Stay tuned for more information from the publisher and its developers.