Why can't my Droid Turbo 2 play media volume?

[AC Question]

On my Droid Turbo 2, the media volume will no longer play on the phone's external speakers. I know the speakers are not the problem because they will still play alarm and ring volume on the phone. When I try to play sound in a video or app the sound will not play, even though I turn it up. How can I fix this problem?