I'm sure this topic has already been resolved, but I'm posting this because I've run into the same problem.
In my case, the problem was that the virtual key input from DS4Windows (by Jays2Kings) was not recognized by DCS World.
The other day, I noticed that when I enabled the Scan code option on DS4Windows, the key input was recognized by DCS World.
DS4Windows seems to be using Win32API's SendInput() for virtual key input.
If you specify the KEYEVENTF_SCANCODE argument, the virtual key will be input in a form that the DCS World can recognize.
In the DS4Windows code, you can use performKeyPress() and performSCKeyPress() to learn how to set the options.
