Incorrect login details used
Login details used by users for FTP access include their username and password. If these credentials are given wrongly in the FTP client, it can give a 530 login error in FTP.
"530 Login authentication failed" also happens due to wrong password. Even a single additional space in the password can cause a login failure. Many account owners tend to overlook that aspect and struggle with 530 errors.
Path doesn't exist
When the FTP users gets created, a path will be assagined on creation. If the path doesn't exists on the server this will cause a login failure.
No TLS used
TLS is required and enforced for security reasons. It's a very bad idea to disable it, since passwords would be sent in cleartext. Make sure to activate "Explicit SSL/TLS" in your FTP client.However, if you need to disable SSL anyway (For example incompatible ERP system that only supports plain text FTP)
