PHP fatal error undefined function

[Tue Feb 09 18:57:35.612710 2016] [:error] [pid 5793] [client 45.33.0.237:56318] PHP Fatal error: Call to undefined function ress_social_sharing_update_counts() in /nas/content/live/dlap/wp-content/plugins/responsive-social-share/inc/classes/wpspec_Caching.php on line 89

https://wordpress.org/plugins/responsive-social-share/