Sorry for the delay
All I meant by “clean log” was that I would stop the Plex Server - most easily done by right clicking the Plex icon in the Windows system tray and selecting Exit
I would then restart the server, wait 1 minute and then start whichever player I was investigating - this just made it easier to find the entries in the log file)
Then the log files can be obtained in 1 single zip file using the Troubleshooting section of the Server settings - see https://support.plex.tv/articles/200250417-plex-media-server-log-files/
I’ve created a new post as I also tried capturing all the various packets flowing between the server and the Sonos One to work out why some files played correctly when requested via Alexa on the Sonos. I found that Alexa-Plex-Sonos worked OK if the files had not been “analysed”. If I analysed the files (which then creates a profile of the loudness) then I get the same error as you see (the Unable to play 'start?X-Plex-Token… message).
You can tell if your files have been analysed by navigating in the web browser to a track and selecting the three dots and “Get Info” This shows a file that had been analysed
To unanalyse you need to remove the media from the library, (either remove the folders from Plex or as test just delete the files - assuming they are backed up) recan the library (and then restart the server to be on the safe side). Add the media back, rescan and then try again with Alexa.
If you have just requested a failed file then you might need to request more than one working file.
I have also disabled Plex for reanalysing the files Settings->Server->Library and then scroll down to Analyse audio files and set to Never. (default setting is as scheduled task )
It would be good to know if your files had been already analsysed and if newly added media works correctly with Alexa on the Sonos One
(This has made no difference to trying to cast Plex from Android to Sonos but the Sonos App does that job OK)
