How to start Plex playlist on Sonos speaker

From the dashboard I am able to use the media player to Browse Media, select the right playlist, and the music will start playing. However, I am unable to get this working in automation form. This is what I have:

service: media_player.play_media
  media_content_type: "plex://{ \"playlist_name\": \"All Music\" }"
  media_content_id: playlist
  enqueue: play
    - media_player.living_room

When I run it, it says “Action run successfully” but nothing plays on the speaker

Have you been able to figure this out? I’m in a similar situation. I can get the Sonos speaker to play from the media player card, but want to figure out a shortcut so my daughter can just play her music playlists. Playlists don’t go the next song using the Plex Meets Home Assistant card unfortunately.

I was excited at first for the speaker in her room until I realized the Sonos app opened up all of the music library (definitely do not want that), and I cannot get her managed user to play to the Sonos through her Plex app unless I want to shell out for more plex passes (already have lifetime on mine), so my next thought was using Home Assistant as I already setup a Symfonisk gen 2 remote for her to use.

I get a log entry
Sonos does not support a media type of ""plex://{ \"playlist_name\": \"4 Plus\" }""
The backslashes aren’t mine, may be added by Developer Tools or something. Now, I am trying this without having a Plex account. I don’t want one as all my content is on a local NAS. From the Media tab I am able to play a playlist on my Sonos speakers without a Plex account, so I expect it can be made to work in an automation, somehow.