Pioneer djm 450 not recording in audacity

Hi
I got my djm 450 yesterday with 2 xdj 1000 and I want to record a mix session in audacity I've followed all the tutorials of how to to do it online and there is still no output from the djm in audacity. It shows up in the line in and everything on my laptop but there's ids just no sound out, I'm using windows 10 and plugging the USB from the back of the mixer into the laptop.
Any help would be great
Many thanks
George