The reason for 530 Login authentication failed:
FileZilla 530 Login authentication failed usually occurs when you are using whether incorrect username, password, hostname or connection port.
The first thing you need to do is make sure you are using relevant and correct username and password when accessing the server. If one of those is incorrect – you’ll definitely get 530 error, so double check if you are using correct credentials. If you are 100% sure that you are using valid credentials – check if the domain is pointed correctly to the server and reset the password.
On the other hand, the problem can be inside FileZilla. Perhaps the login authentication error 530 failed because you have activated unusual encryption mode in the settings. Maybe during the last session, you’ve changed the settings for the sake of interest, which eventually results in incorrect login 530. Then go to the settings in the “Encryption” section and set “Use simple FTP”. And although this is not entirely correct in terms of security, it’s better than not accessing the server at all.
If you are using cPanel – there may be two types of FTP accounts: default and additional (pointed to a certain domain). For default account, the login to FTP is same as username. But the additional FTP accounts are in format «email@example.com», so make sure you are using relevant login details in cPanel.
FTP database corruption
Pure-ftp accounts and users passwords are stored in an encrypted database. It may be corrupted due to incorrect cPanel update or inaccurate FTP server changes. Database corruption may cause even bigger problems, than 530 login authentication errors. The fastest way to solve this problem is switching from pure-ftp to pro-ftp and back – this recovers the database with passwords.