Apple changed the way you rate songs in the Music app in iOS 9.3. It’s not a big change, but I’ve gotten several emails from people trying to rate songs and not being able to do so.
You previously tapped the name of a song or album in the play control section of the Music app to rate a song. Now, tap the artwork, and you’ll see five little dots; tap one of them to apply a rating. For example, tap the fourth dot from the left to rate a song four stars.
Tap anywhere in the artwork area other than on the stars to hide the rating and display the artwork again.
Note that if a song contains lyrics, then the stars display above the lyrics when you tap the album artwork.