1.Edit /etc/ssh/sshd_config with sudo or root privilege

$ sudo vim /etc/ssh/sshd_config

2.Uncomment “#PermitRootLogin without-password”, Add “PermitRootLogin yes”

# Authentication:
LoginGraceTime 120
#PermitRootLogin without-password
PermitRootLogin yes
StrictModes yes

3.Restart SSH Service

# service ssh restart

Or

# systemctl restart ssh