I’ve also restarted PMS and the SONOS controllers, rebooted our BOOST, all to no avail. The weird thing is that these files played maybe 2 days ago(?) without issue. I’ve tried rescanning library files and running PMS’ Analyze function and on the SONOS side, I’ve tried refreshing the music library. I should also mention that these flac files were purchased as “cd-quality” downloads in their current format (I did not rip or convert them in any way). I have one album that is hi-res flac and it plays fine but - as one would expect - only because it is being transcoded to AAC WILL play these problem flac files in a browser tab launched from the Synology dashboard as flac (“Direct Play” in the PMS dashboard). However, all other tracks on the same album fail to play. I have found only 2 flac files that will play and I can see in the PMS dashboard that they are being played as flac (stereo) at 834Kpbs and 941Kbps, respectively. PMS fails to serve up almost all 16bit 44.1kHz flac files to SONOS and reports “Unable to play - the connection to Plex was lost.” This error is reported in both Android and Windows SONOS controllers. PMS will play any mp3 file via either the Android and Windows desktop SONOS controllers (S2).

Unfortunately, both the NAS software (including Disk Station Manager, v: 6.2.4-25556) and PMS (v1.) were updated during this time, so I’m not sure where the issue started, but this is what I’ve been able to establish:

It has been working flawlessly until the last couple of days. I’ve been using PLEX Media Server (PMS) running on a Synology Diskstation to serve up local music files to the household SONOS system.

Plex media server on synology