When working with RDS, I would occasionally find my web console-initiated restores-from-s3 stall out indefinitely with no errors of any kind. Confused, I ran to AWS Support, who told me that I should not specify "root" as the admin user when restoring the database to RDS. This is because the backup already contains a root user, and it was causing the restore to silently fail.
Long story short: never use "root" as the admin user when restoring a MySQL backup to RDS.