If are doing some modifications on Apple Music and no seeing them on iTunes or vice versa, you should try to reset your iTunes / Apple Music. That could be due to the iCloud Music Library not in Sync in your iTunes software. For that:
- Erase not in Sync elements on iTunes (be sure they are existing on Apple Music side before)
- Log out and log in again
- Be sure to enabled iCloud Music Library (new connection)
- Create all playlists (could be not needed as the playlists/metadata could came back to life with the new iCloud Music Library from iTunes)
- Recreate new Synchronizations if you had some
If you still have difference between iTunes and Apple Music, please reach Apple support directly.