Fix #3: Install graphics drivers. Another simple way to fix Dev Error 6066 in Call of Duty Warzone and Modern Warfare is to install the latest graphics drivers.

You need to know how to install and upgrade GPU drivers to keep your graphics card running as fast as possible. Here's how to do it in Windows 10.

To install a graphics card into your PC, you'll need to open its case, remove the existing card, and slide your new card into the PCI Express slot.