I am having a similar issue. I have my music sync’d to my Kyocera and it works fine when I am at home (from the Downloads & Sync Folder) and works when I leave initially. After I have been travelling for a couple days, the data shows that it is still on my device but the Plex app states that there are no files available until I get back onto my WiFi again and then its all there (not re-sync’d). I do not turn on the mobile data option.
Same. Mobile sync broken AGAIN. Content appears to have sync’d but when attempting to play on mobile device get error message. This is SUPER frustrating. Plex Server 4.43.4 Plex for Windows Version 1.23.0.1435-e10e14cf Plex for Android Version 8.8.2.21525 Running on Galaxy Note 20 Ultra Android 10 One UI Version 2.5