With any major OS release, in spite of rigorous testing and numerous developer previews, it's not uncommon for random issues to arise. Some users who've updated their Pixel or Nexus devices to Oreo have discovered an annoying bug whereby the alarm in the Google Clock app simply isn't going off. And that's a pretty big problem if it's the only alarm app you use.
A reader emailed us to say that their Pixel alarm clock has been inconsistent since updating to Oreo, with alarms set to less than an hour ahead sometimes going off and those set further ahead never going off. It seems they are not the only one. Here are some recent reviews from the Play Store listing:
This was great until it stopped working 3 days ago. Suddenly my morning alarm doesn't go off anymore and I was late for work for 3 days running.
Thanks for not setting my God damn alarm off. Now I'm going to have to explain to my boss why I missed work today. Hello iPhone X!
Since the last update, the clock app has been dismissing the alarms as soon as they start to go off. I have noticed if a set an alarm a minute from now it works. When I set an alarm for tomorrow morning it dismisses itself.
Crashes every time the alarm goes off.
After Oreo update alarms no longer go off!!!
I won't bore you with too many of them (there are at least 20 more) as they're all saying basically the same thing: since updating to Oreo my alarm isn't working. A number of users are saying they've been late for work because of it, too, which is no small matter. There's chatter about it on Reddit as well.
None of the AP staff have noticed this issue so far, but it does appear to be fairly widespread. There's nothing much you can do about it for the time being, except wait for Google to acknowledge the issue and work on a fix. In the meantime, you'll have to install a back-up alarm app clock and carry on. My personal favorite for several years has been Sleep as Android, which I use in conjunction with the stock Android app to be extra certain I won't oversleep (although I still do). There are plenty of other good options on the Play Store, too.