Problems

Having issues with the audio alerts. They dont play when wearing headphones. They do play without headphones. Ive tried changing settings around to no avail. Im at a loss to what is wrong. Is it user error or a problem with the app? I was able to use this app with my iPhone 4 with no issues, but now with the iPhone 6, its not working.
with no issues, but

ZombieKillerz about Ease into 5K: run walk interval training program, v3.5.7