If you get the unknown instance message while reloading SSH :
That means that SSH is not running, you have to start it.
sudo /etc/init.d/ssh start
sudo start ssh
sudo stop ssh sudo start ssh
Check if it is working :
ps -ef | grep sshd
root 1234 1 0 12:28 ? 00:00:00 /usr/sbin/sshd -D