cjnords, you might want to try going into Settings > Sound and changing the Text tone or setting for it.
I have a iPhone 6s Plus and the other day the screen would not turn off to sleep. Even though I had it set to 30 seconds in Settings > General > Auto-Lock. I then when into the settings and moved it from 30 sec. to 1 minute then back to 30 sec. And it's been fine since. So apparently was just a temporary glitch in the iOS. Which is the point I'm trying to make.
Another thing that might be worth trying is a sound test from Apple.
Cjnords, We're here to help. We want your device to be fully functional. When did the issue begin? Have you tried a different notification tone?