Q: iOS 10 - Alarm stopped working

I can set multiple alarms and they work as intended. The only problem I have, is that the alarm- and ringtone-sound mute automatically after a few days. (I can't say exactly when) BUT E-Mail, SMS and all other sounds are working normal.

I can't find any volume on my phone that is set lower than 50%. Hardware mute button still isn't active and I tried turning it on/off multiple times. Also airplane mode doesn't help and when I plug in headphones the sound also doesn't work. Never used airplay.

The only solution I have at the moment, is that I change the alarm sound every day before I go to sleep and when there is no "teaser"-sound I turn my phone off and on again... after that procedure I can hear all sounds again.

I am having the exact same problem and issues with the clock app as jrich4945 describes.  I had an iPhone 6S with iOS 9.3.4. that worked perfect.  It was backed up on iCloud regularly including right before I upgraded to an iPhone 7 that already had iOS 10 installed on it.  When I restored from the backup of the iPhone 6S is when the clock app didn't work properly and had all the same issues as described in the beginning post. (Alarms don't vibrate or make sound, timer when set doesn't go off, when change app it resets timer, puts the clock in upper right hand corner even when alarms are turned off, only removes clock when turn phone on and off, all other music, rings, and alert sounds from other apps work as normal with the exception of other alarm clock apps).

I thought that if there was another app I could use as a workaround I would do it but I've tried using 4 different third-party alarm clock apps and they all have the same issue as the Apple Clock app - they won't wake up the phone to play the alarm.  Makes me wonder if these 3rd party alarm apps just use Apple's Clock app in the background to perform their functions?  The one exception is the app Alarm Clock For Me which will kind of work.  If I set an alarm or a timer on that app and then don't shut the screen off or change apps then it will sound the alarm.  But if I shut the screen off or switch to another app the alarm will go off but with no sound or vibration.  Doesn't make me feel very confident that the alarm will go off. 

I have read all the posts in this thread up to this point and have tried all the suggestions here except the complete refresh and start as new phone because like many other people that is not an option for me with over 300 apps and data for many of the apps, messages, etc.  Sure it could be done but the reason I got the original iPhone and every upgraded iPhone since is because of the ease of restoring backups to the new iteration of iPhone.  I'm not spending hours and hours to try to put my phone back in order and don't think I should have to.

That being said I finally setup a genius bar meeting at the local Apple Store to see if the "geniuses" could figure it out.  After 2 hours with 3 different geniuses (including their brightest and most experienced) they basically couldn't figure it out as well.  They ruled out it being a hardware issue, tried other 3rd party alarm apps like I did, did some resets and used diagnostic tools, and looked up their Apple in-house blogs for similar issues.  They told me that Apple's engineers are aware of this issue (probably because of threads like this one) and that until they figure it out and put it in a new iOS 10 update that the only thing I could do is completely reset the phone, set it up as a new iPhone, and manually add all my apps and data in one by one.  UGGHHHHH!!!

So PLEASE Apple can you please take this problem seriously and come up with an update soon!!  I think its amazing all the things my iPhone can do but that it can't do as basic a thing as turn on an alarm to wake me up or alert me to when it's time to flip the food on the grill.  Although a small thing it's kind of an important one as others have pointed out that they made it to work late because of this iOS 10 update.  Think of the productivity and money loss that causes - hopefully no one loses their job over it.  Until then, I guess I'll have to find that old bell alarm clock in the closet or just go back to the 6S with iOS 9 that worked great.

I've had the EXACT same issues all the way down to exactly the experience you described with Alarm Clock for Me. Let's hope they get this fixed sooner than later hopefully with the next update.

Glad to see someone has made some progress - even if it's only temporary. I have tried all these suggestions (except frying my phone!) with no success at all. I hope the info about Apple engineers looking into this is accurate.