Sonos Port/Line Out ... Where's The Sound?

Not sure what Line 2/B is. In general, the Port should act as essentially a tape deck. Try moving your line in from digital coax to the analog output on the Port, using the RCA jacks, which is then connected to the line in on your Onkyo. (It would be helpful to know which model Onkyo, so we could look it up and be sure this advice is worthwhile….some receivers are not capable of connecting with a Sonos Port, due to lack of appropriate inputs/outputs.) The analog input on the Port would then connected to the same device’s output on the Onkyo…just like a tape deck would be. 

Or, depending on the Onkyo (and I have no idea if it can do this), you may just need to ‘marry’ the digital input and that line out 2/B in the Onkyo’s software, so they work in concert. Most devices aren’t looking for input in one location, and sending out data in another…especially second ‘rooms’ on amplifiers, which often only transmit analog inputs, and can’t handle digital (HDMI or other) inputs. 

The Onkyo is TX-NR6100.   I was hoping to play content to both the streaming speakers and the connected bookshelf speakers simultaneously, if that’s even possible.  So you are saying to use two sets of RCA, rather than one digital and one RCA? 
 

What you want achive is the whole point of the Port, so it should be working. When playing from the Port to the receiver the coaxial Digital in should be chosen on the receiver. When playing from the receiver the Line out (Zone 2/Zone B) should be functional (maybe this is a setting in the receiver). Remember many receivers do not convert digital sources to analoque though, so if you are playing HDMI sources (your TV, BD-player etc.) there might be no sound coming out of the Line out.

Thank you.  I will check how I had the Line 2/B set.  I am playing from two analog sources, both are old-school CD players (one is a Pioneer jukebox) that are connected to the receiver with RCA cables.  In the Sonos app, I can see that sound is going to the Port and the grouped speakers, but the sound isn’t coming out of the One SLs.