As for the files not seen by iTunes and MediaMonkey, by evidence the files haven't been added to iTunesCDB, but only to the internal device database.
I guess workround for you would be to re-sync the tracks from MM to the device.
Are you sure that syncing from MM isn't working for you? Just tested iOS 14.3 sync and it is working fine for me (tested both MM4/MM5).
Maybe you just overlooked the track being added (with the amount of the tracks already presented on the device)?
Try to create a small playlist (consisting only from two tracks), right-click the playlist in MediaMonkey > Send to > iPhone
Then go to the device and tap Music > Playlists and locate the playlist synced by MM and its tracks.
If you are sure that the playlist and the tracks aren't there then generate debug log (item 4b here:
viewtopic.php?f=6&t=341 )
As for the files not seen by iTunes and MediaMonkey, by evidence the files haven't been added to iTunesCDB, but only to the internal device database.
I guess workround for you would be to re-sync the tracks from MM to the device.
Are you sure that syncing from MM isn't working for you? Just tested iOS 14.3 sync and it is working fine for me (tested both MM4/MM5).
Maybe you just overlooked the track being added (with the amount of the tracks already presented on the device)?
Try to create a small playlist (consisting only from two tracks), right-click the playlist in MediaMonkey > Send to > iPhone
Then go to the device and tap Music > Playlists and locate the playlist synced by MM and its tracks.
If you are sure that the playlist and the tracks aren't there then generate debug log (item 4b here: https://www.mediamonkey.com/forum/viewtopic.php?f=6&t=341 )