@daller, i just did this and it worked. below is the code i commented out.
/*
* Validate the referer
*/
// $salt = get_option( 'feuprosalt' );
// if( empty( $_SERVER['HTTP_REFERER'] ) || false === get_transient( 'feupro_referer_' . md5( $_SERVER['HTTP_REFERER'] . $salt ) ) )
// {
// if( isset( $settings->debug ) ) Log::write( 'info', 'Failed referer verification' );
// die();
// }
// if( isset( $settings->debug ) ) Log::write( 'info', 'Passed referer' );