Duplicate Error Message No Appearing

Your software
My Mautic version is: 4.4.3
My PHP version is: 7.4.29
My Database type and version is: 10.2.44-MariaDB

Your problem
My problem is:

In the past, when I added a contact manually and added an e-mail address that is already in the system, once I move from the field a message will appear: A contact with that value already exist

That message does not appear and subsequently, I have duplicate e-mail addresses.

How does one resolve this whereby the error message appear when a duplicate e-mail address is added?

These errors are showing in the log:

Steps I have tried to fix the problem: