Activating Support System

When I try to activate the support system , it fails and gives me the error :

Fatal error: Call to undefined function get_current_site() in /home/content/84/7560984/html/wp-content/plugins/incsub-support/incsub-support.php on line 241

The instructions also say to activate from a network plugin panel, but I don't have or need that. Pls help