iPhone alarm does not go off sometimes

Hey there JareB888,

Thanks for reaching out to the Apple Support Communities. To get started, do you have an alarm set up using a sleep schedule, or do you have the alarm set up in the Clock app? If using a sleep schedule, although we understand the the Ringer & Alert volume is turned up, let's ensure that the alarm volume is turned up with the steps shown here: Set an alarm on iPhone - Apple Support

Change the next wake up alarm

The wake up alarm in the Clock app shows the next wake up time in your sleep schedule (if you’ve set up a sleep schedule in the Health app). Although you don’t set the wake up alarm in Clock, you can make changes to it in Clock after you’ve set up a sleep schedule.

1. Tap Alarm, then tap Change.

2. Adjust your sleep and wake times.

Drag  to change your wake up time,  to change your bedtime, or the semicircle between the icons to shift both times simultaneously.

3. Scroll down to Alarm Options, then change any of the following:

- Alarm: Tap to turn the alarm off or on.

- Sounds & Haptics: Tap to choose a vibration or ringtone.

- Alarm volume: Drag the slider.

- Snooze: Turn on to give yourself a few more minutes of sleep.

If the alarm is set up in the Clock app, does the issue persist if you remove and readd the alarm?

Let us know what you find, and we'll continue from there.

Cheers!