Apple Music not syncing across devices

There seems to be an ongoing issue with Apple Music for some users where changes made on a computer don't get uploaded to the iCloud Music Library, and are later reverted. Results may be better immediately after rebooting, and/or if you disable Home Sharing. Hopefully this issue will be resolved in the next OS release.

tt2

Hey there clemenchuchu,

Thanks for reaching out to Apple Support Communities. We understanding your iMac will not sync your music. We're happy to provide some assistance.

Let's first make sure all of your devices are associated to the same Apple ID. This is required to sync music across devices. Once done, let's make sure the "Sync Library" option is enabled as outlined here:

On your Mac

Open the Apple Music app.

From the menu bar at the top of your screen, choose Music > Preferences.

Go to the General tab and select Sync Library to turn it on. If you don't subscribe to Apple Music or iTunes Match, you won’t see an option to turn on Sync Library.

Click OK.

If you have a large music library, it might take some time to upload and sync your music library across all of your devices.

Also, is your Mac up-to-date? Updating your software can potentially resolve unexpected issue:

Update macOS on Mac

If the issue persists, was anything updated or changed when you first noticed this? Are you subscribed to Apple Music or iTunes Match? Do you purchase your music on iTunes? This will help us determine how to proceed.

Keep us posted.

Have a great day!