Appointments + causing a fatal error

Hi, I recently moved my network over to WP Engine, I'v e been having an issue with the Appointments + Plugin causing a fatal error and causing the sites using it to "white out" Any recommendations ion what to do to make this work??

"PHP Fatal error: Cannot redeclare class google_signer in /nas/wp/www/cluster-2788/businesslink/wp-content/plugins/appointments/includes/gcal/auth/Google_Signer.php on line 28"