After running the command as you have mentioned and installing the SSL Plugin again I got the below mentioned message:-
Really Simple SSL failed to detect a valid SSL certificate. If you do have an SSL certificate, try to reload this page over https by clicking this button:
Reload over https
. The built-in certificate check will run once daily, to force a new certificate check visit the SSL settings page. Really Simple SSL requires a valid SSL certificate. You can check your certificate on Qualys SSL Labs.
While I Reload over https, the messsege I am getting
Your connection is not private. Problem not rectified