Start by updating your iPhone 11 to iOS 16.3.1, which is the latest version.
You can check your current version here:
Settings → General → About
You can download and install software updates here:
Settings → General → Software Update
You can find more useful information here:
Update your iPhone or iPad - Apple Support
Check if you have Do Not Disturb or another Focus profile activated. Also check if one of the profiles activates automatically, as this can cause unexpected problems with receiving notifications.
Start by disabling the active Focus profile if it is active. You can do this in the Control Center. Pull the Control Center down from the top right corner. Find the Focus Button, just below Screen Rotate Lock and Screen Mirror, tap and deactivate the active profile.
If Do Not Disturb or another Focus profile activates automatically, then a Schedule is active.
To disable or delete this schedule, go to:
Settings → Focus → Select Profile → find SET A SCHEDULE → Tap into the time → tap Delete Schedule or just deactivate.
You can read more about how to use Focus here:
Use Focus on your iPhone or iPad - Apple Support