Notifications on iPhone 11 no more functional

I had two problems: No notification sound nor show as unopened. After checking all settings, I did hard reboot and it resolved. Quick up volume, down volume, then hold side button till apple icon reappears (20 secs).

Second, when I send myself a message, like texting myself a note from notes or sending myself a screenshot, I no longer get a notification nor does it show as an unopened message. This maybe a change in iOS, but to me it’s a problem.

Check if you have Do Not Disturb enabled. Pull up your Control Center from the bottom and look for the Focus/Do Not Disturb button. Tap in and disable the feature.

If you find that Do Not Disturb activates itself, then a Schedule is activated, or Smart Activation is activated.

Go to Settings → Focus → Do Not Disturb

Scroll down and find Schedule, or Turn on Automatically. Tap on your set times and select "Delete Schedule" When the list is empty, Do Not Disturb will not activate automatically anymore.

You can read more about the Focus functions here:

Use Focus on your iPhone or iPad - Apple Support

Yes, always take a Backup before resetting anything, just to be safe. If you have an old iCloud Backup that you think you don't need, then you can delete them to make room for a new one. Alternatively, you can upgrade to iCloud+, so you get more space in iCloud.

If you only select is Reset All Settings, then your content will not be deleted, but all settings will be set back to when you turned on the phone for the first time. I suggest you choose that option first.

If you select Erase All Content and Settings, then ALL content will be deleted, all settings will be reset and the phone will start up like the first time you took it out of the box. Wait to do this.

How to upgrade to iCloud+

Upgrade to iCloud+ - Apple Support

You can check your iCloud Backup here:

Settings → Apple ID → iCloud → Manage Account Storage → Backup

If your new copy is there, then your iPhone is Backed Up.

Also remember to activate Photos, Contacts, etc. in Settings → Apple ID → iCloud.

Reset All Settings won't "wipe" your iPhone of all your content, but it's good to be proactive in case something goes wrong anyway.

Also review this Support Article:

How to back up your iPhone or iPad with iCloud - Apple Support