I don’t use Sonos playlists myself as I prefer to create them in either my music service providers native app (Amazon Music mainly), or use .m3u playlists in my locally held NAS shared library and have both types feed through automatically to Sonos, however I have seen some others mention this issue with Sonos playlists here in the community, but not seen anyone yet say they have contacted Sonos Support to inform them of the issue, so not sure if Sonos are aware at the moment. It maybe worth reporting this perhaps? Here is the link to maybe give ‘em a call…

https://support.sonos.com/s/contact

Hi you need to go into systems settings then into  manage, scroll down to and click on Music Library and there it will give you details on how to share your music library with sonos.

It took me several attempts to put my music on the sonos app and found that I have had to use my external drive to do the share as that is where my music is stored.  I have tried to transfer them to my computer but it wouldnt transfer so I am happy to do it via my external hard drive as long as I can play all my music that were vinyl, cd's, tape and minidisc that are now digitalised.  Its taken a while since the app upgrade but I am now happy with how I have been able to set it up.

Thank you. These were playlists I created on the Sonos app, so they are not on my devices nor are they in my streaming services. They have just disappeared. Frustrating. But I don’t see it addressed anywhere. 

SONOS Playlists are still alive and well, stored in the players. Temporarily, the SONOS pad/phone App’s cannot access them. I expect that this will be addressed with a future update. Meanwhile, the Windows desktop controller can access the Playlists.