UPDATE: 7.1.1 seems to have fixed this issue for me.
NOTE: The purpose of this post is to inform. Hopefully the info contained will help some people to not miss work!
I've been having an issue with my phone's sound randomly cutting out. This issue was first noticed one morning when my alarms didn't have sound. Thank god the sound of my phone vibrating woke me up or I'd have missed work.
A bit of tech detective work brought up the fact that this wasn't just my alarm not working, this was my phone not playing sound at all.
I googled the problem and found that others are indeed having this problem, and not just with three same model phones. This further reinforces that it must be an Android OS issue.
I posted my experience on an Android forum. I will copy and paste that here:
I'm having the same issue on my Nexus 6p. Here's my experience:
When the issue mysteriously presents itself, my alarms don't have sound, my timers don't have sound, playing videos through my media app gives me an error claiming the app cannot play that file type, playing music doesn't work, YouTube videos don't have sound, my phone doesn't make the little blip noise when I lock and unlock it... Basically sound doesn't work on my phone. Period.
As a PC technician (but not an Android expert) I have, of course, instantly deduced that turning it off and on again fixes it. But it happens here and there, seemingly at random. I can always tell when my alarm won't work by listening for the blip sound when I lock my phone for the night.
I have a weird lingering feeling that this is somehow linked to Google Now's "Ok Google" detection. I think it happens as I use the voice detection more frequently. But I may be imagining correlation where there is none. It's hard to say since I have never directly seen what straight up causes it.
Whatever the case, this is certainly not the fault of any single app, this looks to me like a bug in the OS.
I just updated to Nougat 7.1.1. No issues yet since the update. I saw nothing mentioning this issue in the patch notes, but I'm crossing my fingers that it got fixed somehow.