Pro Sites Paypal Error Message

I am getting the following error when you click the PayPal button to purchase a pro site level. Any idea of what the issue is, or how I can fix it?

Fatal error: Call to a member function get_error_message() on a non-object in /home/thetheol/public_html/synesisenterprises.com/wp-content/plugins/pro-sites/pro-sites-files/gateways/gateway-paypal-express-pro.php on line 2127