wp-ecommerce fedex shipping not working

hello there,
Am trying to integrate wp-ecommerce with fedex shipping , am not able to receive fedex webservice response , kindly help me to solve this problem.
Note :
i have installed gold cart plugin as per the documentation , correctly filled the fedex form fields ( like meter number , access key etc. )

version details :
worpress Version 3.8.1,
Gold cart Version 2.9.7.7

https://wordpress.org/plugins/wp-e-commerce/