Execution of request failed In google API(Email Creation)

Question

AppsService service = new AppsService(domainname, adminuser, adminpassword); 
service.RetrieveUser(uid);



At the time of Retrieve one error is throwing that->

Execution of request failed:   https://apps-apis.google.com/a/feeds/domain/user/2.0/username


Please Give me a exact solution for this->  I enabled the Admin sdk in admin console