¡ DOOOOOOO NOT RESET ALL YOUR SETTING!
3 Step Method... will fix the alarm app until Apple can maybe do something right with an update (Hint... You fix one thing, and 30 other things fail!
Check your work before you give it to the public, maybe).
1. Turn the Alarm App off > Douple tap The home button, flick the app upwards with your finger.
2. Hard Rest your iPhone > Hold BOTH the on/off button AND the home button until you see the Apple (It may take like 15 seconds, so don't let go)
3.THIS IS THE IMPORTANT ONE!!! Open the Reminders App and set a new reminder WITH an alarm for five minutes BEFORE you want your alarm
to go off.
OKay, now double check your alarm app and make sure that the alarm didn't magically turn itself off (for some reason it does that sometimes when you do a hard reset).
You ou may be asking, what's the point of the Reminders alarm? Well, you can just use that alarm if it'll wake you up... It totally doesn't for me. But the problem with your alarm app since the last update is the Fing alarm goes to sleep! So, since the Reminders app doesn't have the same glitch, you're essentially using it to wake up your phone, so your phone will wake you up (AGAIN! Until Apple gets this fixed). yeah, you may notice that sometimes the alarm vibrates once when it's supposed to turn on, then stops... There's no alarm OR message on your phone that it went off. but every time you go and set you alarm to make sure it works, it goes off fine... just not when you need it too. So, yes... The reminder alarm basically warms-up/ wakes-up your phone... Your alarm will sound off after those steps for sure!
And yeah, Apple Tech Help might wanna read what this guy has to say...