Automate file system playlist on a button

I’ve got an m3u playlist on media that Media Player can see…
filesystem_smb–LBAprYaX://track/0-playlists/Alan Parsons.m3u

If I try and put it in the action for …
Media Play: Play Media
Content ID (as above)
Content Type - playlist
…but it gives…
Failed to perform the action media_player/play_media. [50@0] {load} No such playlist
…so I’m obviously missing something in the URL that I’m passing.

Grateful for help as to how I get the missing piece please.