I got it to work by finding and deleting: tv.plex.providers.epg.cloud**** and files ending in db, shm, wal. There were 2 sets of these files located in: users>***>AppData>local>Plex Media Server>Plug-in Support>databases.
Not sure why it worked – but I guess it forced Plex to find the HDHomerun Quatro and load and update the channel listing. Not sure why there wouldn’t have been a different error message indicating what needed to be done. But as soon as deleting the tv.plex.proviers*** it found the tuner.
