Here's one from our forums that we've been hearing. A lot. And experiencing ourselves as well.
If your phone's been updated to Android 5.0 Lollipop and it's using Google's new interruptions scheme — that is, All, Priority and None — you might find yourself selecting "None" and using it as a way to mute your phone. I've done it. I still do it. But there's a big catch.
Why can't my alarm sound when I have it on mute since the lollipop update?
When you choose "None" for your interruption settings, nothing comes through. Period. And that includes alarms. And to be fair, at least in its stock form, you're warned that this is the case.
So, you've got a few options. One is to use the priority mode, which we've detailed here. That lets you whitelist what comes through — and alarms are always whitelisted.
Our other recommendation is going for about $9 on Amazon.