SOLVED! - Cause of Alexa->-Plex->Sonos problems

So do you confirm that Plex has not analyzed this file ?
i.e. if younavigate to the track in Plex and select “… Get Info” there is no loudness information?

This is controlled in the server by Settings->Library (and scroll down)

Just rechecked and “Alexa ask Plex to play …” worked first time on ,my Sonos One