attached the CD Player L & R on channel A and changed the input on Deck A. I also can see the meters ‘detecting sound’ on Deck A in the preferences window, but I can’t get or hear the music out over the channel A on the S4..
You need to set it as “Live Input”, but only decks C & D can be configured to use external sound sources. Reroute the CD players to the lower decks and assign them that way.