Have you done a recent OS upgrade? Sometimes OS upgrades, particularly with mobile products, result in compatibility issues with software/hardware. I just had one with iOS 9.2 and music/voice recording software on my iPad. Worked fine before that OS and Apple had to apply fixes in 9.3 before it worked again.
Of course, when it first happened, I thought the problem was on the software's side, not Apple's; but turns out it was an Apple-side error. I don't use an iPhone, but a friend who does with that same software experienced the same issue.
However, if no other iPhone users are having the same problem, then....
(Formerly) 2015 MKC 2.3 AWD Reserve
Midnight Sapphire Metallic - White Sands/Espresso interior
THX | Tech Pkg. | Climate Pkg. | 19" Wheels
Build date: July 2014