Can't play any music off-line from iPhone
Apple Music made some fundamental changes to the way the Music app works (when enabled). You now have your entire Apple Music Library in the cloud so that it is accessible from all your devices. With this, all of that content is not automatically downloaded to your device, and in fact, the opposite can occur as Apple uploads music to their cloud. 

So now, you must specifically download whatever content you would like to listen to offline. To do that, open the Music app and navigate to a playlist, album, artist, or song that you would like to download. Now select the "..." (ellipsis menu icon) and choose "Make Available Offline". After the songs download, an icon will display next to each one indicating that it is available for offline listening.



You can also download your tracks directly from the album/playlist view: