FeedBlitz offers as part of our Feedburner Migration process, the ability to log directly into the Feedburner account to access the RSS and email subscribers available.
Some publishers have run into "Login Failed" when trying to log into their Feedburner account through FeedBlitz.
If the publisher has verified the username and password are correct and login fails, the publisher most likely has 2-step verification or two-factor authentication enabled in their Google account.
2-steps verification greatly increases the security for the account by sending a code to your phone when logging into Google services, but this prevents FeedBlitz from accessing the Feedburner account and delays the migration process.
Before any publisher starts the Feedburner Migration, we would ask that 2-step verification be temporarily disabled until we have secured your subscribers.