Apple - "Playlist can't be added to your iCloud Music Library". Why?

"Playlists that reference other Playlists can not be uploaded"

It took me awhile to figure out the solution to this problem, but I eventually did. You can no longer just drag and drop songs from Apple Playlists to new ones that you create yourself, but you are still able to do it a different way. You also used to be able to just right-click on a song, a menu would pop up, and you could then "add to selected playlist" - this no longer works either.

Solution: if you go into any one of your Apple Music playlists, hover over any one of the songs, you will notice a little icon with 3 dots show up - if you LEFT-click on this, a menu will pop up (different than the old menu), and then add the song to your desired new self-made playlist. This seems to work.

The problem is that iTunes still has both the old method and the new method active, but only the new method actually works.

This is what finally worked for me.

1. Create a new playlist, and copy all songs from the problem playlist
2. In playlist, remove all downloads. I did this by highlighting all songs, clicking on ..., and selecting 'remove download'.
3. This make the download from iCloud icon appear next to all the songs
4. Then I had to go through and click each song to get it to redownload from iCloud. About 10% of my songs would not download from iCloud.
5. I moved the 10% of bad songs to a temporary playlist and deleted them from the new playlist. The new playlist would now sync to iCloud.
6. I then dragged and dropped each song, 1 by 1, from the temp playlist back into my new playlist. It wouldn't work if a dragged more than 1 at a time.
7. After doing that, my new playlist synced to iCloud and all my devices.

I saw this error when I added songs directly from the "For You" or "New" tabs in iTunes to a playlist.

To fix the error for my playlist I manually added the songs to My Library, then added them to a playlist. I was then able to sync that playlist.