Certain tracks won't play on iPhone

[Bsanch]

Some tracks from the Josh Garrels album "Love & War & The Sea In Between" won't play on my iPhone.  They work fine on my desktop, and show up black on playlist on phone yet they just won't play.  I have them downloaded also for offline play.  I tried rebooting phone but that wouldn't work.  I'm wondering if uninstalling app is the way to go but I'm hesitant because of all the tracks I have set to play offline.  Any suggestions?