I'm DJing my first wedding on Sunday!
Obviously I'm using Cross and my U-Mix Control Pro 2

and I have lots of music in my library to play.
But I was hoping that I could route audio from my Mac headphone jack into the UMCP2. I have a cable plugged into my Mac that on the other end plugging into Input 1/2 on the UMCP2.
When I select "Line" as the source in Cross I hear silence. I was expecting to hear the audio from Spotify/my Mac.
Tracks played through Cross normally are heard fine via output 1/2 that goes out to an amp and speakers.
Am I misunderstanding how the Line should work? I'm using Dual Stereo. Input 1/2 is set to output through 1/2. The switch on the back of Input 1/2 is set to Line. I've tried Phono in both Cross and on the UMCP2 and still silence.
I'm sure I used to play Vinyl's straight through Cross this way.
Help?!
EDIT: Screenshots:
http://puu.sh/oyDr3/588fe620ee.pngMac with headphone socket/cable, USB is portable HDD -
http://puu.sh/oyDFA/c6c3c705aa.pngUMCP2 USB to Mac, cables in back of UMCP2 -
http://puu.sh/oyDDp/b9eae9436c.png