Describe your network; router, repeaters, pods, etc.  Also, any VPN software you may be running. 

Sonos needs a good network to function properly and there are requirements you need to have in order for this to happen. These requirements can be found here: 

https://support.sonos.com/en-us/article/sonos-system-requirements

it would help others is the community to provide suggestions fix your issues if you provide more inform about your network. 

Hi, my Sonos soundbar and sub are about three feet from a wifi router. AirPlay worked, then didn’t. I restarted devices, including struggling with setup of the sub again which included repeated setup failed errors for no obvious reason. I tried Ethernet from the arc to the router (has 4 LAN ports). In all cases I am able to play music fine to Sonos, using the Sonos app. This to me absolutely confirms no network issue.
 

What I have been unable to do for weeks now is AirPlay, which was a deal breaker for this purchase. I simply would not have bought Sonos gear without reliable Airplay, which the marketing lies presented as a given. And it’s not just me.. Google tells the same story. A lot of anger out there. 
 

I work in IT as a programmer and am very familiar with networks, routing etc. yet I am at a loss here. No way someone should be messing round with MAC addresses or otherwise for this s*** to just work. Certainly plugging in an Ethernet cable should’ve been immediately job done.

Moderator Note: Modified in accordance with the Community Code of Conduct.

When you say you can’t Airplay, are the speakers showing up in Apple Music but you’re just unable to get them to play? Or are the speakers not showing up? 

Also, when did you last turn off your phone?

Have you checked for firmware updates? There was one released last week that you should install.

But, from the new information you have provided, you may have an issues with your phone and not Sonos. I would suggest a complete reboot of everything, including you phone, following these steps:

Power off everything - Sonos, router/network and phone.

Starting with your router/network, power it on and allow it to fully boot.

Then power on the Arc allowing it to fully boot before you power on the Sub

Power on your phone and connect to your system. Check Airplay functionality.

Something else that came to mind is, if you are using BETA software on your iPhone, that will cause issues with Sonos as well.