Sleep schedule alarm is silent if AirPods were connected and died
I have found that my phone does not make any noise if an alarm is set through the Health > Sleep > Sleep Schedule alarm system if AirPods are playing audio or if AirPods were playing audio but ran out of batter overnight.
I sleep with my AirPods Pro 2 in every night for noise canceling and a sleep podcast. This causes alarms set through the Sleep Schedule to not sound. The phone will have the alarm screen on, but neither the phone or AirPods make any noise. If the AirPods ran out of battery overnight, the phone will not make any noise for an alarm. But even if the AirPods do still have battery and are playing music or a podcast, there is still no noise for an alarm through the phone speaker or the AirPods. Alarms set through the Clock app do not have this issue.
iPhone 14 Pro