Premium Extensions Suddenly Stopped Working

I have two sites with paid-for Premium Extensions that have been working find, but suddenly stopped working last week. Both sites are asking me to pay again even though the license is only 1 month old.

Both sites were upgraded that week to WordPress 3.6.1

Both are using WPB2D 1.6.1

http://wordpress.org/plugins/wordpress-backup-to-dropbox/