ReportViewer returns "The request failed with an empty response."

Hi

I use report viewer in my asp.net mvc app as below :

 ReportViewer viewer = new ReportViewer
            {
                ProcessingMode = ProcessingMode.Remote,
                //AsyncRendering = true,
                //EnableTheming = true,
                ShowCredentialPrompts = false,
            };
            viewer.ServerReport.ReportServerUrl = new Uri(ConfigurationManager.AppSettings["ReportserverUrl"]);
            viewer.ServerReport.ReportPath = $"/report/{reportName}";
            //viewer.ProcessingMode = ProcessingMode.Remote;
            viewer.ServerReport.ReportServerCredentials.NetworkCredentials=new NetworkCredential("888888","8888", "888888");

            ReportParameter[] param = new ReportParameter[1];
            param[0] = new ReportParameter("UserId", userId.ToString());

           
            viewer.ShowParameterPrompts = false;
            viewer.ServerReport.SetParameters(param);
            
            viewer.ServerReport.Refresh();

The report server is located in other location with different IP. But when the code reaches "SetParameters" it throws the following error :

"The request failed with an empty response."

I checked the SSRS logs but could not find anything. I tried SSRs web portal and could view the report. 

 I changed NetworkCredential to some wrong values and got Unauthorized error, So I don`t think there would be a problem with authentication. 

Would you guide me ?