the issue is within sshd_config file

1. Login as root to Ubuntu server (or droplet)
2. Use vim or nano to edit the contents /etc/ssh/sshd_config

  # vi /etc/ssh/sshd_config
  # nano /etc/ssh/sshd_config

3. Now go to the very between of the file (to the line PasswordAuthentication)

    # Change to no to disable tunnelled clear text passwords
    PasswordAuthentication yes
   

4. Save the file and reload the SSH config:

   sudo service sshd reload