On the first startup of Nero Start, you may log in with some email address other than the one you entered during purchasing Nero software on Nero website.
These are the steps about how to log out:
1. In the top right corner, click the third icon. Dropdown menu will be shown.
2. Click Sign Out.
3. In the popup dialog, click 'Yes, sign out' button.
4. Then relog in with the email address you entered during purchasing.