AW2720HF, 17 R3, no audio?

I have an Alienware 27" AW2720HF connected to my 17 R3 laptop. But Alienware Command Center says it doesn't pick up any compatible devices?

The AW2720HF is linked via the HDMI cable, I can see the Dell Nvidia High Definition Sound Driver in my sound options, but I get no sound out of the monitor when I switch to this.

I have downloaded drivers, run the auto fix from windows and I get nothing. The really odd thing is that my old screen which is not Dell or Alienware, works fine with the Nvidia High Definition Audio Device setting. 

So how do I get this to work?

The AW2720HF does not have built-in speakers. Are you testing headphones in the Headphone port? Or external powered speakers in the Line-out port?
DELL-Admin