Master Volume is disabled, even though it is not

Just bought a DDJ-RB and I am trying to use the PC Master Out feature but whenever I try to change the master volume (top right corner) I get the Master Volume is disabled - control the master volume with the connected DJ equipment message, even though the button is lit.

I have re-installed all the audio driver and the "High Definition Speakers" are not even showing in here either.

any suggestions?

Thanks in advance.