Not getting response when I call "2/files/listfolder" method

Hi

I am using RestClient.

HTTP client is not overriding at my side. I got authorize and token successfully.

I am using following code for get list of folders:

RestClient restClient = new RestClient("https://api.dropboxapi.com");

private IRestResponse executeRequest(RestRequest request)
{
            var iy = GetTokenInfo(ref status, ref errMsg);
            if (status == "OK" && errMsg == ")
            {
                restClient.Authenticator = new HttpBasicAuthenticator(clientId, clientSecret);
            }
          
            request.AddHeader("Authorization", "Bearer " + accessToken);
            request.AddHeader("Content-Type", "application/json");
            return restClient.Execute(request);
 }

  private RestRequest FormRequest(RestType rtype, string data, Boolean useXML)
        {
            Method method;
            switch (rtype)
            {
                case RestType.Get:
                    method = Method.GET;
                    break;
                case RestType.Post:
                    method = Method.POST;
                    break;
                case RestType.Put:
                    method = Method.PUT;
                    break;
                case RestType.Delete:
                    method = Method.DELETE;
                    break;

                default: return null;
            }

            RestRequest request = new RestRequest(data, method);

            if (useXML)
                request.AddHeader("Accept", "application/xml");
            else
                request.AddHeader("Accept", "application/json");

            return request;
        }

And list of folders:-

 public string GetMetaData(string path, ref string status, ref string errMsg)
        {
            string responseStr = ";
            string url = "/2/files/list_folder";
            RestType type = RestType.Post;
            Boolean useXml = false;
            RestRequest request = FormRequest(type, url, useXml);
            request.AddParameter("path", path);
            //request.AddParameter("include_media_info", false);
            //request.AddParameter("include_deleted", false);
            IRestResponse response;
            try
            {
                response = executeRequest(request);
                responseStr = response.Content;
                status = response.StatusDescription;
            }
            catch (Exception ex)
            {
                errMsg = ex.Message;
                return null;
            }
            return responseStr;
        }

And again I got same error as I sent to yesterday.

Please suggest me.