Edited: Clearing app data & cache doesn't fix problem. Voice is notorious for not ringing. I previously found a fix, but with the latest updates, phone won't ring unless unlocked. When locked, it just vibrates. I think the problem is that Voice notifications can only be set with notification sounds, while my actual ringtone settings will only let me select ringtone sounds. When these don't match up, Voice won't ring. Can confirm that I fixed a different phone (OnePlus) by matching up sound files