I am actually undergoing the same technical difficulties.
Only my Majesty will ring for incoming calls, will make sounds when I type, and will even vibrate for my notifications. However it will not make a sound to let me know I have notifications, waiting to be responded to.. I've checked every setting that has to do with sounds and notifications, but they all say my volume is at a Max. It is really beginning to get to me. I've downloaded apps, restarted my phone, re-activated my phone, even changed my notifications ringtone and absolutely Nothing.