Crystal Reports prompt issue on export: “The report you requested requires further information”

I have searched through forums for a solution but none seem to work for me.

I have an ASP Webform/MySql application which displays Crystal Reports.

The ones which do not require a user to enter a parameter display fine and I am able to click on export on the CR toolbar and download, e.g. .pdf format.

On the report that require a user to enter a parameter, the report renders fine but when I click on the export button, i get the prompt:

"The report you requested requires further information"

asking for DB login credentials. How can I avoid this?

My Code:

 protected void Page_Load(object sender, EventArgs e)
        {
            if (Request.QueryString["report"] != null)
            {
                string reportToGet = Convert.ToString(Request.QueryString["report"]);

                switch (reportToGet)
                {
                    case "payslip":
                        PaySlip();
                        break;
                    case "pastpayslip":
                        PanelPastPaySlip.Visible = true;
                        break;
                    case "paysummary":

                        break;
                    case "pastpaysummary":

                        break;
                    default:
                        break;
                }
            }
        }

 protected void btnSearch_Click(object sender, EventArgs e)
 {
      if (txtDate.Text != null || txtDate.Text != string.Empty)
           if (DateTime.TryParseExact(txtDate.Text, "yyyy-MM-dd", CultureInfo.InvariantCulture,
                       DateTimeStyles.None, out date))
               PastPaySlip();
 }

private void PastPaySlip()
{
      // Some code.....
      PayMasterDataSetTableAdapters.pastpayslipcasualviewTableAdapter ta =
                new PayMasterDataSetTableAdapters.pastpayslipcasualviewTableAdapter();
      PayMasterDataSet.pastpayslipcasualviewDataTable dt = new PayMasterDataSet.pastpayslipcasualviewDataTable();
                ta.FillBy(dt, userId, businessId);           

      cReport = new ReportDocument();
      string reportPath = Server.MapPath("~/Views/CasualLabour/Reports/PastPaySlip.rpt");
      cReport.Load(reportPath);
      cReport.SetDataSource((DataTable)dt);
      cReport.SetParameterValue("Date", date);
      CrystalReportViewer1.ReportSource = cReport;
      CrystalReportViewer1.ReuseParameterValuesOnRefresh = true;