register page: Fatal error

Why does this come on register page?

Fatal error: Uncaught SoapFault exception: [WSDL] SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://api.apptivo.com/app/services/v1/BusinessSiteServices?wsdl' : failed to load external entity "https://api.apptivo.com/app/services/v1/BusinessSiteServices?wsdl" in C:\xampp\htdocs\wordpress\wp-content\plugins\apptivo-ecommerce\classes\countries.class.php:320 Stack trace: #0 C:\xampp\htdocs\wordpress\wp-content\plugins\apptivo-ecommerce\classes\countries.class.php(320): SoapClient->SoapClient('https://api.app...') #1 C:\xampp\htdocs\wordpress\wp-content\plugins\apptivo-ecommerce\classes\register.class.php(142): apptivo_ecommerce_countries->get_countries() #2 C:\xampp\htdocs\wordpress\wp-content\plugins\apptivo-ecommerce\classes\register.class.php(98): apptivo_ecommerce_register->register_form_field('register_countr...', Array) #3 [internal function]: apptivo_ecommerce_register->apptivo_register('') #4 C:\xampp\htdocs\wordpress\wp-includes\plugin.php(406): call_user_func_array(Array, Array) #5 C:\xampp\htdocs\wordpress\wp in C:\xampp\htdocs\wordpress\wp-content\plugins\apptivo-ecommerce\classes\countries.class.php on line 320<blockquote></blockquote><blockquote></blockquote>

what should i do to fix it?

thanks 🙂

http://wordpress.org/extend/plugins/apptivo-ecommerce/