Seems odd, the Sonos is designed, on its line in RCA ports, to accept any line level signal from the Denon. What set of outputs on your Denon do you have the line in on your Sonos Port? 

Which customer service phone number did you call? What was the name of the person you spoke with? I’m guessing they need more training, or simply didn’t understand what your issue was.

Thanks for your response. I have tried all three sets of audio outs on my Denon reciever:  VCR1, VCR2/aux and tape.  None worked with inputs from TV, which are digital to the receiver. I read somewhere during my searches today that some receivers do not convert digital audio signals into analog audio out signals, so maybe that’s my problem.  I was able to get a very weak output from a Bluetooth device attached with RCA cables to input on my receiver, but the output was barely audible and it was on a delay from the audio from the passive speakers attached to the receiver.

I used the customer service number provided in the support contact in the Sonos app. 

I suspect you’re right, most digital inputs (at least in many receivers) are not converted to analog outputs. You could probably test this, if the receiver’s manual is not available, by playing an analog outputs, such as a turntable, or radio, rather than the digital inputs you’ve been trying. 

If it were me, and the option were available, I’d keep the Port wired to the Tape loop on the receiver, so you could use tape out on the receiver to line in on the Port, and then tape in on the receiver connected to line out on the Port, so information could travel both ways. 

Without details on who you spoke with, I don’t know if Sonos will be able to do extra training with that specific rep. I can say that the few times I’ve needed to call in, the person I’ve spoken to was both knowledgeable and helpful, you may want to try calling again.

I don’t know which vintage receiver you are using. Very modern receivers don’t usually understand tape decks. If your receiver supports a tape deck, pretend that PORT is a three head cassette deck that is recording the receiver’s radio, phono, etc., then “monitor” the recording. This will work around the inherent latency between PORT’s Line-In and output from a SONOS player.

If the receiver has a Zone2 analog output, connect this to Line-In because receiver digital inputs will be converted to analog for Zone2.

I can not audio output from my TV (digital) through my receiver to the Port, but the other analog outputs from my receiver worked and I was able to use Port to connect to my other Sonos speakers with audio content FROM my receiver. The advice to use tape in and tape out was good advice and makes sense. Thank you for the assistance.