Reply to Crossfader Isses when Master Output is Laptop Speakers

Hi,

Once I put laptop speakers as the master output, the crossfader on my DENON MC300 would not work.
It only works when I cue music on my headphones. Once the music is played live on laptop speakers,the crossfader function does not work.

I have gone onto traktor pro 2 and ticked yes to showing the crossfader. I have made sure Decks A and B have been highlighted.

I still don't understand what is wrong. Please healp!