Email as Username

Hello
I have just now configured my site to use 'Email as Username'.  I can see where the wording on the login form and profile page has changed from Username to Email, but it will not accept an email to login using users that are already set up in Membership Pro.  I have set the Joomla Username to be able to be changed.   I Note the comment "Ony able to be used with users who have signed up with Membership Pro'.  My members have signed up with Membership Pro in the past - others have been migrated into MembershipPro.  Am I missing a step?  
Thanks

Hello Elaine

For this, we will have to check it directly on your site. Please submit a support ticket sending us:

1. Super admin account of the site
2. Link to the page to login
3. Send us the account which you are using to login and get this error

We will check to see what's wrong and get it sorted

Regards,

Tuan