I’ve read a few cases where people did not have the internal preamp on their turntable set to on. Can you check this on your Sony?

Thanks for the reply. I looked this up on various sites, and they all talk about the inbuilt preamp so I’m still a bit confused. I have tried pairing it with the 5 but it doesn’t seem to pick it up either. 

Pairing (via bluetooth) won’t work since only the Sonos Move does bluetooth.

“No sound” is not a good sign. Low volume can be a problem if the internal amp isn’t turned on. If you take a look at page 8 of the manual:

The Output select switch should be set to Line.

Here’s how to choose the right input in the Sonos app: https://support.sonos.com/s/article/4837?language=en_US

That’s really helpful - I’ve got sound now! However, I am using one Sonos 5 only, and it feels like it is playing an album out of one channel only. Is there anything in settings to change, so that I can hear it fully? (Currently can’t hear the singer but can hear the band singing the chorus)

Many thanks. 

Btw, the 5 is placed horizontally. 

The Sonos Five should play stereo when placed horizontally. I'd check the cables if I where you. Are they seated right? What adapter cable are you using? Here's what Sonos says about connecteing sources to the Five: https://support.sonos.com/s/article/4837?language=en_US

Along the lines of what 106ralleye suggest, you may also want to be certain the cable on use is stereo to stereo, and not stereo to mono.