iPhone sleep/wake up alarm goes silently

I've been using the new "bedtime" alarm since it came out, . But suddenly it isn't working. I wake up and look at my phone and it LOOKS like the alarm is going off, but there's no sound! Yes the switch is set to mute and I have do not disturb on, but I have always had them set like that, and it worked! I don't know why it's changed.

My phone us updated to the latest iOS version, volume in “sounds and haptics” is set to the maximum, “change with buttons” is disabled. My alarm from the clock app is set to the maximum volume as well.

any tips on how to fix this?