Could not save user due to invalid email address (Attribute Mapping Issue):

To create a new user in the Joomla email address is mandatory.

In your case you are facing the issue to create user either of the following reason.

1. You are not receiving the email address from IDP in any attribute name.
   Solution: Your IDP should send the email address to our Joomla SP plugin.
2. You are not receiving the email address in the NameID attribute.
   Solution: Click on the Quick Fix button to perform the SSO.