warning message when registering a new site

I am getting a warning message on the front end of my sub-site when trying to register a new site.

Warning: call_user_func() expects parameter 1 to be a valid callback, class 'ProSites_Module_BulkUpgrades' does not have a method 'render_gateway' in /home/ecyp/public_html/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/View/Front/Gateway.php on line 136