Hi @BenjiAroundtheWorld 

Welcome to the Sonos Community!

If AirPlay is inactive for a time, the connection may be lost (though it’s not indicated). Sometimes you can force it by pressing Play either in the Sonos app or on the speaker.

Otherwise, disconnecting and reconnecting AirPlay should solve it.

If behaviour is inconsistent (or if AirPlay doesn’t connect) it would be worth giving your router a reboot by switching it off for 30 seconds, and repeating this several times a year (especially if your router came for free from your Internet Provider).

I hope this helps!

Thanks for your reply but no it’s not working. If I disconnect and reconnect I don’t have sound. I checked the volume and try that but it’s not working. The only way to make it work again is to restart the computer. And after a while I get the same problem. 
With my phone I can connect / disconnect with no problem.

Any idea ?

How to AirPlay music on Mac

Ok, so there are multiple ways to do this, some more obvious than others. While iTunes now supports AirPlay 2, there might be times you'll want to stream audio from other programs or from the browser – a podcast on YouTube, for example.

The good news is that you can mirror the audio from your Mac; however (for now) this only works on the original AirPlay protocol, meaning you can only stream to one speaker at a time. It's possible Apple will open this up to all system audio in the future.

The above is from https://www.the-ambient.com/how-to/use-airplay-on-mac-1578#

I suspect your Mac is using Airplay 1, not Airplay 2.  Sonos does not support Airplay 1 (because Airplay 1 was, is and forever will be crap)..

I’m having this exact same issue! AirPlay from macOS almost never works, both from the music app and the system audio. It works perfectly with my Ones. No problem with my iOS devices either.

That certainly suggests an issue with Apple’s implementation of AirPlay 2 some devices. I’d recommend reaching out to Apple directly, if it works consistently from your iOS devices.

I am having essentially the same issue: I want to stream system audio (actually, content from the TV app or YouTube in a browser, but as opposed to selecting the sound output in the Music app) from an M1 MacBook Air to my Sonos Move, and it works over Bluetooth, but even while showing it is connected using AirPlay 2, it is silent. I am pretty sure I have got it to work in the past so I am going to say this is intermittent, but persistent. 

I should have read the thread more carefully: yes, this can be fixed with a restart and then immediately starting the connection, but I have found a pause of just a few minutes can break it. I have submitted feedback to April *but you will also have a developer relations team that is presumably participating in WWDC next month and will be well-placed to raise this.* I would ask that Sonos makes its developers aware. In my public beta feedback I am suggesting that if may screen sleep that causes it, but this is circumstantial / coincidental.

A workaround on the Move is to use Bluetooth, of course, but it is inelegant.