https://pdf-services-ue1.adobe.io/assets generating forbidden error 403 invalid client id

the bove code in c++ using microsoft c++rest sdk

std::string CWbssecurity::Adobeassetuploadid(std::string accesstoken, std::string clientid, std::string requestid)
{
std::shared_ptr<std::string> rtn = std::shared_ptr<std::string>(new std::string());

try
{

std::string otpuri = "https://pdf-services.adobe.io/assets";

utility::string_t otpuris = utility::conversions::to_string_t(otpuri);

web::uri uri(utility::conversions::to_string_t(otpuris));
web::uri_builder uri_builder(uri);
web::http::client::http_client client(uri);
web::http::http_request request2(web::http::methods::POST);

std::string contype = "application/json";
utility::string_t ctype = utility::conversions::to_string_t(contype);

request2.headers().set_content_type(ctype);

std::string auth = "Authorization";
utility::string_t autht = utility::conversions::to_string_t(auth);
std::string bearer = "Bearer " + accesstoken;
request2.headers().add(autht, bearer.c_str());

std::string apikey = "X-API-KeyRequired";
utility::string_t apikeys = utility::conversions::to_string_t(apikey);
request2.headers().add(apikeys, clientid.c_str());

std::string payload;
payload = "{\"mediatype\": \"application/pdf\"}";

utility::string_t body = utility::conversions::to_string_t(payload);

request2.set_body(body);
client.request(request2).then([rtn](web::http::http_response response2)
{

*rtn = utility::conversions::to_utf8string(response2.extract_string(true).get());

CString msg;
msg.Format(_T("St: %d"), response2.status_code());
AfxMessageBox((CString)rtn->c_str() + msg);

}).wait();
}
catch (web::http::http_exception e)
{
AfxMessageBox((CString)(e.what()));
}
return(*rtn);
}