My mother-in-law's iPad Mini stopped ringing for incoming FaceTime calls. Bearing in mind that she's 90, and lives in Mexico, and her first language is Russian, I phoned to walk her through the usual issues. Mute is off, Do Not Disturb is off, master volume is maxed, alert volume is maxed, Notification settings are correct. Slide switch is set to rotation. She gets sound *in* FaceTime, as well as YouTube, Siri, etc., but no ringer, key or lock sounds. I had her shut down and restart. I had her do a hard restart (Power + Home buttons). The only thing I could not verify was the mute condition on her Control Center, because a leather cover apparently prevents swiping up from the bottom. I'm sure she doesn't know what Control Center is and has never seen it. I think she's using iOS 8. I'm out of ideas.