VSFTPD 530 Login incorrect
vi /etc/pam.d/vsftp
comment #auth required pam_shells.so
and then
service vsftpd restartpam_shells.so means that only users with shells access should be allowed so that's why needs to be commented.
Does the user have a valid shell? I think it has to be in the /etc/shells list. Is the user definitely not the file /etc/vsftpd/ftpusers?
Make sure you definitely editing /etc/vsftpd/vsftpd.conf , that bit me on CentOS I was editing /etc/vsftpd.conf .
vsftpd can be a bit fiddly and is not great at reporting errors. Stick with it I was tearing my hair out at with a very similar problem, its always a simple solution.