I have DK2 running fine on my system

I use Logitech G35 7.1 surround headphones.

DK1 audio works fine, Mentor voice is present.

DK2, all audio is fine in the "Audio Settings" screen, I can eve hear the Mentor Voice when grabbing the VOICE slider.
It says "One.....Two....." etc

However, in the game, the Mentor voice is absent

NONE of the threads in this forum has solved the problem

Can someone fix this? And I mean beyond suggesting "I uninstalled it, and reinstalled it, and now it works"

Solutions like that are USELESS.

I hope I'm not too late to be helpful with this, but I had this problem and fixed it by changing the Sound option from "Headphones" to "Stereo". For some reason, it fixed it. No idea why. I hope this helps. :)