HostSEO servers block remote connection to xmlrpc.php or, wp-cron.php for security reason. Thats why you may find difficulties to install Jetpack and WP Super Cache plugin in Wordpress Scripts. To overcome this, just add the following lines into your .htaccess and then try to install these plugins.
<FilesMatch "^(wp-cron|xmlrpc).php$">
order allow,deny
allow from all
</FilesMatch>
