No notification sounds since iOS 11.7

Great inconvenience and embarrassment has resulted from my inability to get audible notifications on my iPhone. I get vibrations, but no sounds. This appears to be the case for all types of notifications turned on, but the most serious issue is no sounds for messaging (SMS and iMessage). Phone call rings and alarms work fine.

• Messages | Allow Notifications ON
• Messages | Critical Alerts ON
• Messages | Time Sensitive Notifications ON
• Messages | Alerts | Lock Screen, Notification Center, Banners. (Alerts display on the lock screen)
• Messages | Notification Grouping AUTOMATIC
• Messages | Sounds | Classic | Minuet (sounds when selected)
• Messages | Customize Messages | Repeat Alerts ONCE (also tried twice)
• Messages | Customize Messages | Unknown Senders ON
• Messages | Customize Messages | Emergency Contact Alerts ON

All was well on my iPhone 13 until I installed iOS 11.7 after which notification sounds stopped, and the problem persists still at 18.1.1.

I have tried every suggestion online, checking app notification settings, selected sounds (tried many) even to the point of resetting the phone to factory default and restoring data (what a mess that was to recover from!).

One complication is that I have hearing aids and use the Smart 3D app to get all the sounds redirected to my hearing aids. However, uninstalling that app made no difference, nor does turning off the hearing aids that also puts sounds back on the phone speaker. And again, it's just notifications, not rings and other sounds.

I am at my wits end.

Note: My wife and I got our phones at the same time and have the same iOS version; hers works OK.