XDJ RX3 with DVS (Interface 2)

Hi, I just bought a xdj rx3 and although I know it doesn't have in built dvs, I bought an interface 2 soundcard to use with sit similar to the demo video below with the RX2. https://m.youtube.com/watch?v=l9VBelB6iow I have everything setup but when I change the input to line, no sound comes through. It's set to relative mode and the line inputs work fine with the usb unplugged. I'm fairly familiar with dvs systems and don't think I'm missing anything as it's a straightforward setup. Any help would be appreciated. Thanks John-Paul