iMessage Notifications Not Working for iOS 26 iPhone 17

iMessage alert notifications (sound) stopped working consistently when iOS was updated to 26. Issue started on my iPhone 13 with the upgrade to iOS 26 and persists even though I just moved to an iPhone 17. I do not have Focus turned on. Sound is turned up. Shutting the phone off and back on helps temporarily for a few received messages, but then the alert stops again. I can change the alert tone, and again, the sound works for a few messages and then stops. I turned on WiFi calling - sound worked for new messages then stopped again. HELP please!!