This right here IS THE FIX. So heres what happened to me.
The other day Apple music (on my iphone) said login even though I was. This is because they now want you to login with your Apple ID and not your Beats username (if you had beats first). Beats or not, this will fix your issue.
Now because Music cloud based to sync with your itunes they don't automatically turn on cloud sharing on your phone. This is a good thing because people would complain that their music/data is being moved around without them knowing first, so do what @fredmuito said:
Solution.
You have to authorize your iCloud Library.
Go to Settings > Music > iCloud Library - Turn it on.
Even though I lost all my subscription music and playlists (temporarily), the second I turned on iCloud in settings and everything came back instantly. I know its scary but everyone needs to calm down with the negative words. Its a brand new app, the app in INCREDIBLE, it has TONS of great features, and its beautiful. I have used premium Spotify and Pandora for so many years. Here is a great example of a feature that none of those can do.
1. Find a song on the radio (or on anything other than your phone)
2. On your iphone ask Siri "What song is this?"
3. Click on the song once it comes up
4. It brings up the entire album in Music and you can add the song/album to your playlist
Pretty darn cool. Give it a chance because its changing the game.
Please push "This helped me" below if it helped you because it took me forever to figure this out and now my Music is perfect and will be from this point on. Thanks @fredmuito