After installing DisplayFusionSetup-9.4-Beta4.exe, my wallpaper colors dissapears on both 4K monitors.
The same thing happened on a 2nd computer. Monitor Configuration no longer shows Wallpaper, and Desktop Wallpaper only shows full physical monitor screens, which are all black. You can only change the color of the entire monitor, NOT DF monitors.
After reinstalling DisplayFusionSetup-9.3c.exe on both computers, everything starting working again.