Consider the scenario :- SSH service in your server ( CPanel ) has falied and its not allowing you to login from backend. But you can login to WHM with any issues. Trying to restart SSH using WHM > Restart Services also is giving a “Failed” result .

or

You have changed the SSH port for server hardening , but forgot to add the new port to the firewall rules. And after you logout from the current shell you cant login using both ports: -

Please paste the following to your browser

http://your_server_ip:2086/scripts2/doautofixer?autofix=safesshrestart

This will reset the current SSH configuration to default configuration and safely restart SSH. As you all know this only works on a Cpanel Server!

Source : http://gnusys.net/ssh-service-failed-and-you-cant-start-it-using-cpanel/