I want to add a couple songs to an iCloud Music Library playlist (in iTunes 18.104.22.168 on OS X 10.10.5), but the songs aren't in my iCloud Music Library:
If I right-click on the songs and select "Add to iCloud Music Library", the "spinner" appears in the upper-right corner of the iTunes window and shortly afterwards disappears. The songs continue to have the cloud icon with the slash through it:
I guess it's failing without displaying an error message. I get the same message (as above) when I again try to add the songs to the playlist.
I tried forcing an update as described in https://apple.stackexchange.com/a/197896/94, and I also tried signing out and back in and (again) forcing an update.
How can I get more information on why these songs are failing to sync to my iCloud Music Library?