Hi, as you have mentioned all the notification sounds are turned on and you have checked all the volume settings but still the issue persists, then try to perform Safe mode.
Boting your device in Safe Mode will essentially disable all 3rd party apps/services and purely load the Android OS.
To enter Safe Mode, please perform the following:
1.First, completely power off the phone.
2. Then, power on the phone and when the Samsung logo appears, press and hold down the Volume down key.
3.If done correctly, "Safe Mode" will display on the bottom left corner of the screen. If "Safe Mode" does not appear, repeat the steps above.
4.Once you are in Safe Mode, you can remove the third-party app that is causing issues on your phone.
5.To exit Safe Mode, simply restart your phone and it will reboot normally.
If the issue still persists then please perform backup and factory reset by following the steps in the given links.