It's either you didn't set it up right or it's defective.
CD changer? As if it won't play CDs? I read the docs and it tells me it plays CDs so I called it a player. I won't edit my replies to call it as a changer. I think you can live with that.
I tried replying to R. Proffit's reply about my hookups for the Changer, I've tried the RCA (red&white), the optical, and the digital coax, all hooked up from the changer to the back of the Soundbar which you were correct has an X in the model #.
Let me mention that the Onkyo DXC390 is a CD changer, not a CD player.