Thank you ALL for the well thought out suggestions based on what I furnished you…. I finally resolved it and learned something though I’m not sure I can explain it all…
In the SONOS APP, I have the “Music Library” pointed at my Synology 920+ which has a dedicated folder with all my 1600+ Songs.
When I scroll to the Group, and then the new single song, I was repeatedly met with the dreaded 88,100 Pop UP that it was not compatible. No other file presented this error to my knowledge, though I did not test every song.
As I Updated the Music Library after each file replacement with a new version after countless transcoding's, I saw at the bottom of the SONOS Library list under Artist, Album, etc. a “Folders” option. I opened that and it shows the address link to my NAS. Clicking on it, I’m presented with all the folders in the Music folder. Same Music, just not categorized other than the folder name. Clicking on the Group, then THAT Song…. and it PLAYS! I went back a few steps to the categories and again clicked on the SAME song and it failed to play and again with the same 88,100 Error.
Going directly into the File Folder on the NAS, I checked the “Recycle Bin and it was empty. I’ve learned in the past that the Recycle Bin, if it contains anything, SONOS will present it as just another file… SONOS doesn’t know it’s a Recycle Bin and ignore it.
So what was it seeing? Some time ago I learned about the advantage of enacting Synology “Snapshots” is “a point-in-time copy stored in the same volume used to record the whole data status at the time upon being taken.” I had set it to store the latest 6 Snapshots…. These Snapshots have not been an issue, nor do I need to actively maintain them.. its automatic. But why the issue with this one file? I took a chance and Deleted all 6 Snapshots (60gb+)…. I then clicked on the previously unplayable song… and it worked! I was unaware the Snapshots could even be accessed as its meant to be a secure backup.
The 88,100 led me to believe it was encoded in a non-SONOS codec… Why it presented that I don’t know. And that original file that never worked is fine and its the one that I am now using.
But it works, and I’ve learned another lesson…
Thanks again….