Reply to Laptop output into S4 (C or D) output, aint working no more...

Macbook Pro + S4

The other day I had a gig. I setup the unit at home with the rental PA's to ensure that everything is working. I tested to ensure that iTunes can run through my D channel (for when dinner time comes) and to my surprise without even doing anything fancy, it did. I plugged in a 2.5 to RCA (into S4) and it just worked - all good until I rebooted.

So I get to the gig and after setting up and trying to access my iTunes through the same setup at home, it didn't work. I tried different RCA's, messing with settings and everything else I could believe of but the headphone to RCA, simply didn't want to work. The only way that I got it to work was changing my sound output preferences in my OSX to S4 which simply used the USB.

Now, at home, before I left I was using the headphone jack (output of macbook) to RCA input on the S4 - the only thing I did was reboot which I hadn't done in about a week. So is there any way of having the audio feed into my S4 through input C and D again? Did I do something wrong? Am I missing something?

The main reason I need this is so that I can have my banquet hall dinners in peace, play the dinner playlist off of iTubes and then when I am ready to get the ball rolling, be able to press play on the S4 and fade out itunes via deck C or D.

Cheers!