Doesnt work for iPhone 6s

I used this app all the time on my iPhone 4s and it worked great. It had a good variety of tuning option for multiple instruments and I used it all the time. I got my iPhone 6s a while ago and this app is making a buzzing sound each time I try to use it. Instead of it picking up my guitar string, it picks up the sound of the buzzing. Its really irritating and I cannot use this app anymore. I would use it again if they would fix the problem but its starting to seem like Im the only one having this issue.

TheMiniDiamond about Fine Tuner - Chromatic Tuner