Execution of request failed In google API(Email Creation)

[Sabir As]

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