Hi @GraziaCunningha,

As you have discovered, the default email address and login information in Canvas are two different things.  Sometimes the login info will be an email address, but it could also just be a username, depending how your Canvas instance is configured.  In this case, you'll need to modify the login info, which you can do following the  How do I manage a user's login information in an a... - Instructure Community - 232  guide.  You can either add a second login, or edit the existing login and just change the login field from the old email to the new one.

Hope this helps!

-Chris