Well, I have a long story about this, plus the solution.
One day I turn on my iPhone and get the message "Subscribe to Apple Music!" I was already subscribed, so I clicked on the link to see what happens. Sure enough, it tells me that I am already subscribed. I think nothing of it until later, when I find most of my music (mostly ripped from my own CDs) grayed out and the message Abdulziz quotes, "Item not available."
I tried to sync. It would not sync. I tried restoring the software on my iPhone. Still would not sync. So I called Apple and was on the phone with a senior advisor for six hours with a few short breaks. She could not solve it. Sent a program to record processes on my computer and said she would send it to software engineers and get back to me within 48 hours. (She also promised me a $100 gift certificate when it was solved).
No reply after 48 hours. I called Apple, and they said the engineers were still working on it. So I tried a few things myself. First I tried using home sharing to move the music. No dice, the little moving circle got hung up halfway through. I tried sharing the music to an old computer I have, and then syncing my iPhone. The music shared ok, but again would not sync (got hung up on "Preparing to copy," or "Applying changes.")
This told me that the problem was with my iPhone or my music library. I plugged a (very) old iPod touch into my computer to see if it would sync my iTunes library. Sure enough, in 10 minutes the whole library was synced. Then I tried it with my iPad. Again, 10 minutes did it.
So I plugged in my iPhone, clicked "Restore software," and then "Restore as new iPhone." I ALSO declined to copy settings (which was the difference from the first restore). Then, as soon as the iPhone was responding at all, I synced all of my music successfully. I made sure "Show Apple Music" was off, and that "iCloud music" was off. I will never use either of those two monsters again!! Then I completed the sync and added my apps back, and now everything works.
Apple reports that software engineers are still working on it, even though i told them it is solved. They will not give me my $100 until the engineers check in.
I'm going to subscribe to Spotify.