tested with "free" version....now have different paid version: Can't add members becuase "email address already in use"

tested with "free" version....now have different paid version: Can't add members becuase "email address already in use"

I can't add users to our CRM, because I previously had a "test" ZOHO CRM, and invited certain users to it.  Now, I want to add them to our paid company version, but can't because their email was used in the other free version, which is now deleted (yes, I completely deleted that account).

??    Obviously, I need to add our employees to the CRM as users.    What's the fix or workaround?