Alarm not making a sound and volume is all the way up

Go to Settings > Sounds & Haptics. Under Ringtone and Alert Volume, drag the slider to the left or right to set the volume. While you're dragging the slider, an alert will sound, so you can hear how the volume changes. Turn on Change with Buttons to use the volume buttons on your device to change the alarm volume.4 days ago

How to set and change alarms on your iPhone - Apple Support

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If the alarm volume is too low or quiet

Do Not Disturb, the Ring/Silent switch and Silent mode don't affect the alarm sound. If you use the Ring/Silent switch or Action button to turn on Silent mode or turn on Do Not Disturb, the alarm still sounds.

If your alarm doesn't sound or is too quiet, or if your iPhone only vibrates, check the following:

• Set the volume on your iPhone. If your alarm volume is too low or too loud, press the volume up or volume down button to adjust it. You can also go to Settings > Sounds & Haptics and drag the slider under Ringtone and Alert Volume.
• If your alarm only vibrates, make sure your alarm sound isn't set to None. Open the Clock app, tap the Alarms tab, then tap Edit. Tap the alarm, then tap Sound and choose a Sound.
• If you connect headphones to your iPhone, the alarm will play at a set volume through the built-in speakers on your iPhone as well as wired and wireless headphones.
• When you use StandBy, haptics for your alarms are disabled. To make sure that your alarm sound isn't set to None: open the Clock app, tap the Alarms tab, then tap Edit. Tap the alarm, then tap Sound and choose a Sound.

Manually adjusting the time on your iPhone in Settings to change app behaviour, such as game timers, isn’t recommended and can affect alarms."