If you have enabled Memcached in cPanel, but the caching option is still inactive for your website, check and enable the PHP memcache module through PHP Manager by SuperHosting.
First make sure that Memcached is enabled in cPanel -> Memcached Manager by SuperHosting.
Then check if the PHP memcache module is activated from cPanel -> PHP Manager by SuperHosting.
To enable the PHP memcache module, you need to access PHP Manager by SuperHosting -> PHP modules management. Then select the memcache module (or memcache308 - version 3.0.8) and save your changes.
If you're using WordPress, you need to access the website's administration, reload the Performance menu and check if the Memcached option is already active.