Hi @Mary1387 @Susan151
At this stage my devices have not lost sound notification, so I, too, am simply offering support.
However, when that happened to many people including myself, previously, I found that after a couple of weeks the notification sounds mysteriously started happening again on my phone and iPad 🙂
It helped, though, that while the distinct Airbnb chime was dead quiet, my incoming emails still beeped on arrival with my chosen sound...and because I looked at them asap, I was always aware of reservations straight away.