By examining the screenshot below, you can observe that the error message indicates that the email address has been previously registered.
If you attempt to locate this email using the search function, you will not see any corresponding records.
The error arises because the system detects an email address that is already in use for another user's login. In order to identify which account is associated with the email address, kindly use the ‘Login’ field in UGR.
This will allow you to subsequently modify the username field to a different email address, thus making the email ID available for use.