Fatal error: Call to undefined method stdClass::increase_download_count

Did everything as described and get this error:

Fatal error: Call to undefined method stdClass::increase_download_count() in /home/semperfi/public_html/Randall/wp-content/plugins/email-before-download/download.php on line 167

link: http://semperfistudios.com/Randall/test/

https://wordpress.org/plugins/email-before-download/