IOS – Music player sometimes skips all songs and won’t play

Only the iTunes app is currently able to add songs to the Music app on an iPhone/iPad. This leaves you with the following options

• Play the songs in the Amazon Cloud Player only
• Download them on your main computer and sync via iTunes. Maybe remove them from the Amazon Cloud Player to save storage space

Found the answer! This feature is invisible and you have to know it's there.

To shuffle songs within a genre in your library, do the following:

1. Tap the "My Music" tab.

2. Tap the selection in the divider at the top between "Recently Added" and the music list. A drop down will appear where you can select a means to sort. Select "Genre". You can use this same method to shuffle within other sorting schemes (artists, albums, etc.)

3. Scroll to your desired Genre. Tap the IMAGE (or gray square) to the left of the Genre name, not the name itself. A song within that genre should start to play.

4. When you tap the currently playing song name at the bottom, the currently playing song will expand up. Make sure the Shuffle icon is lit at the bottom.

5. THAT'S IT! Enjoy! If you have the "repeat" icon de-selected, playback will stop once all the songs in the selected genre have been played.

Source (apple forum): https://discussions.apple.com/thread/7106074?tstart=0