I had similar experience as well. They upgraded their client and server software something like 5 years ago which put forward different restrictions on character set used for password. I have used a special character which was no longer allowed. When I needed to restore files after disk failure I could not log in either in the app or on the website. The customer service was useless -- we are sorry, your fault. I have lost 1 TB of personal photos due to this as a paying customer. Never trust Backblaze.