As a guess, you’ve got some network issues, but I’m not 100% sure if it’s between the speakers and your router, or your controller and your router, or perhaps both. That data is stored on your speakers, and not the controller.

It might be best if you were to submit a diagnostic and contact Sonos, but it wouldn’t hurt to refresh your network by unplugging all Sonos devices from power, and while they’re unplugged, reboot your router. Once the router comes back up, you can plug back in your Sonos devices. It might not hurt to power off your iPhones, too, before you reboot the router, and also power them back up afterwards. 

What kind of playlist? A Sonos playlist (shows under Favorites / My Sonos) and is stored on every speaker, or an m3u-type playlist, stored as a file on your NAS somewhere?

Thank you for all for all of the replies.

Almost all of my SONOS components are wired to a TP-Link Managed Ethernet switch that has been properly configured for STP / RSTP per SONOS recommendations. 

Prior to the V14 update everything worked correctly.

I have rebooted everything (SONOS, Modem, Ethernet Switches, NAS and iPhones) numerous times. Do you know of a way to reboot the SONOS components via the internal webpages?  

These are SONOS playlist that show up under My Sonos Playlist

There was a bug a while back where the Sonos app would not show playlists (on iOS), maybe it has come back? Can you try the Sonos app on a different platform?

Try my iOS app (see profile), it will let you export your Sonos playlists into other formats. If it can’t see this particular playlist, then it is gone.

I just tried it on my Microsoft Windows 10 x64 Dell Computer, and it brings up the Playlist immediately. Once the Playlist is selected the icons for each song also appear.

All of my iPhones and iPads are having issues. They have all been updated to iOS 15.3.

I’d repeat my encouragement to give Sonos hard data to look at, so that they might be able to see this bug, and work on it. Anecdotal evidence, in my experience, doesn’t really move engineers. 

Or perhaps Sonos will see something completely different, and provide you that as an answer. 

I have been working with the SONOS technical support team and they had me uninstall and reinstall the SONOS iPhone app. This fixed the issue for a day, but the Playlist is not showing up again. tonight. I will be calling them again tomorrow and adding to the open case.

Still having issues and SONOS has gone silent on indicating when this will be fixed.