How to play Music from a Denon RCD-N12 upon Sonos Group via Port

I have a new Denon CEOL RCD-N12.  I want to play the audio from the CD and radio issued by this little receiver over my Sonos Group (1xBeam, 2xSonos One SL’s and a Sonos Subwoofer + a new Sonos Port).

I’ve tested the new Denon with wired speakers and headphones.  I can hear audio on both.  I disconnected the wired speakers and the headphones. 

To hear the music from the Denon on my Sonos set up, I purchased the Port. 

So far, it does not work.  Here is what I did:

1. I grouped all the Sonos equipment.
2. I connected the Denon and Port as follows;
   1. Denon’s “Audio Out” RCA  to Port’s “Line-In” RCA
3. On the Sonos App the Port’s Line-Out Level is set to ‘Fixed’.

I spent about 90mins with Sonos support and sent them a diagnostic report.  They concluded that the Port was working just fine but was seeing no input from anything. 

So, what am I doing wrong?  Is what I am hoping to do even feasible?

I have not tested the ‘Audio Out’ RCA on the Denon as I dunno how to - I have no other sources I could use to test it with.  I suppose it could be faulty but this device is brand new.

Appreciate any wisdom.