By default the root’s ssh remote shell access is denied by default.
Any attempt to remote login as root will result in
Permission denied message:
firstname.lastname@example.org's password: Permission denied, please try again.
The following config will guide you through the process of enabling SSH root login on Ubuntu/CentOS
Step 1: Open config file
Step 2: Change line:
FROM: PermitRootLogin prohibit-password TO: PermitRootLogin yes
Step 3: Restart service
systemctl restart sshd
After you restart sshd daemon you will be able to remotely login as a root user