Please follow this KB word by word: https://kb.netapp.com/support/index?page=content&id=1012617
If you miss or mis-spel any of the words in /etc/password and /etc/group files, you will receive an error like "Mon Mar 7 04:06:42 GMT [sshd_0:info]: Failed password for sftpuser from 192.168.0.60 port 51543ssh2"
Make sure that the UID and GID specified in passwd and group files are valid. and the option "sftp.auth_style" is set to "unix"