The standard alarm starts 20 minutes before your wakeup time because of the pre-light so it will only fire on the same day if you schedule it 21 minutes in advance.
For testing purposes we recommend to disable all rising times and forerun times for light, sound and vibration in the alarm settings so you can see the effects immediately. For example a back screen at beginning is hard to distinguish from an off screen.
The alarm might be suppressed by a battery optimization of your device manufacturer. Check in your android settings if there is a battery optimization menu and disable optimization for the app.
Here you can find instructions for specific device manufacturers:
If you did not get a warning about an existing battery optimization then please send a message using “Send Feedback” in the app settings about it.The alarm might be suppressed by your do not disturb mode. If you are using a „do not disturb“ mode in the time where the alarm should fire be sure to set it either to “Alarms only” or add an exception for the app in Android settings.
The alarm might be suppressed because notifications are not fully enabled for the app. Check in your Android settings in notification settings for the app if there are submenus for the notification which control display and sound suppression. Enable all of them.
If you have verified that all settings are correct and that you have the latest version of the app and the alarm still does not fire then send a message using “Send Feedback” in the app settings about it.