RDLC Subreport can no show

Question

I am working with RDLC reports and currently I have a sub report with its properties and parameters within a main report. After trying to generate the report, the below error is shown at the UI : "Data retrieval failed for the subreport, 'Subreport1', located at: [C:/filepath]" There is nothing error shown at Visual studio, so I thing the error may not cause by the code. I think the error comes from the parameters at rdlc not being able to pass into the sub report via the main report . Below is my code:

public ReportViewer Main_Report(string path, ProgressReportFilter item, DataTable dt)
 {
                 ReportViewer reportViewer = new ReportViewer();
                 try
                 {
        
                     var user = UserAccess.GetCurrentUser();
                     reportViewer.ProcessingMode = ProcessingMode.Local;
                     //reportViewer.LocalReport.ReportPath = @"Reports/Main_Report.rdlc";
                     reportViewer.LocalReport.ReportPath = path;
                     reportViewer.SizeToReportContent = true;
                     reportViewer.Width = Unit.Percentage(100);
                     reportViewer.Width = Unit.Percentage(100);
                     reportViewer.LocalReport.SetParameters(new Microsoft.Reporting.WebForms.ReportParameter("Year", item.yyyy));
                     reportViewer.LocalReport.SetParameters(new 
                        Microsoft.Reporting.WebForms.ReportParameter("Month", item.mm));
        
                     ReportDataSource ds = new ReportDataSource("Main_DataSet", dt);
        
                     reportViewer.LocalReport.DataSources.Add(ds);
        
                     reportViewer.LocalReport.SubreportProcessing += new 
                         SubreportProcessingEventHandler(Detail_Alco);
                     reportViewer.LocalReport.Refresh();
                 }
                 catch (Exception e)
                 {}
                 return reportViewer;
             }
    
        void Detail_Alco(object sender, SubreportProcessingEventArgs e)
         {
             Helper.log.Info("para is  " + e.Parameters[0].Values[0]);
    
    
             string serial = e.Parameters["serial"].Values[0].ToString();
    
             //Helper.log.Info("serial is " + serial);
    
             Dictionary<string, object> parameters = new Dictionary<string, object>();
               
             parameters.Add("@serial", serial);
    
    
             string spName1 = "SP_Report_MRS_Detail_Breakdown_Report_Sub_Alco";
             SUSDB susdb = new SUSDB();
    
             DataTable dtAlco = ReportHelp.ToDataTable(susdb.DetailBreakdownReport_SubReport_Alco(spName1, parameters));
    
             ReportDataSource ds = new ReportDataSource("Detail_Breakdown_Alco", dtAlco);
    
             e.DataSources.Add(ds);
          }

Any help would be appreciated, many thanks