If you have questions about  where to find the License Key this page may help you.

You can find  your license key in Account section when you login to   https://www.wpbackitup.com/ site.  Please follow the screenshots below:


Look and Click " View Licenses"  

WP BackItUp Account

Look for the  key icon   to  view your License Key

WP BackItUp View License

NOTE: If you need further assistance Please contact WP BackItUp Support and submit a ticket.