DJM-S5 - Constand Problems Working this Mixer.

I don't even know where to begin.  I'm an old school DJ with 1210s and always Numark mixers.  I don't do gigs anymore, just things for myself in the house.  I've been trying to just start with this mixer and it's one issue after another.  Yesterday I was able to play Seralto with the time coded records on both turntables.  I was only able to play vinyl with the right.  Today I disconnected it and figured out I needed to slide the switch in the back to Phone/Line.  I did this and now back to two vinyls, but now I don't have Seralto MP3s access.  What is wrong with this mixer or am I doing something incorrect?  Please I need someone to lend me a hand.  I have to DJ for an Air Force Retirement as a favor and even though I don't want to, I told the Col I would do the favor.  Please anyone I'm happy to even share my phone to make this easier.