I had an issue where a user could not log in via FTP and the log would show:
The user password contained several special characters, like $, ( and two @'s. Changing the password to a simpler string allowed the user to log in via FTP again.
I guess there is a bug with certain characters in passwords.
USER someuser: no such user found from xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx) to yyy.yyy.yyy.yyy:21
The user password contained several special characters, like $, ( and two @'s. Changing the password to a simpler string allowed the user to log in via FTP again.
I guess there is a bug with certain characters in passwords.