Getting "Internal Service Error" in Invitation API for LinkedIn

Question

I am using LinkedInShare library for authentication and I'm getting all information of user's profile.

I am passing following permissions at the time of authentication

r_fullprofile, r_network, r_emailaddress, w_share, w_messages

I'm Program Partner of LinkedIn and I have access to all this to all this permissions and I want to send invitation to other LinkedIn user from my app using linkedin id of linkedin user.

Here's details of my request with parameters:

URL:https://api.linkedin.com/v1/people/~/mailbox

Parameters:

{
    body = "I'd like to add you to my professional network on LinkedIn!";
    "item-content" =     {
        "invitation-request" =         {
            authorization =             {
                name = "NAME_SEARCH";
                value = DNZy;
            };
            "connect-type" = friend;
        };
    };
    recipients =     {
        values =         (
                        {
                person =                 {
                    "_path" = "/people/linkedIn-id";
                };
            }
        );
    };
    subject = "Invitation to connect!";
}

when i execute this i'm getting following error:

{
    errorCode = 0;
    message = "Internal service error";
    requestId = E31HKE6KM7;
    status = 500;
    timestamp = 1474549122972;
}

I also went through whole Invitation API of LinkedIn but i'm not getting that what am I doing wrong here?

If anyone got any idea about this issue then kindly help.

All suggestions are welcomed. Thanks in advance.