Crystal Report: Failed to load from data database - crystal-reports

Question

I am using this code but gives me this error:
Failed to retrieve data from the database. Details: [Database Vendor Code: 201 ]
public JsonResult ReportCertificateOfEmployment(int EmployeeId, int SigId, string SigPosition)
{
string Userkey = "gHeOai6bFzWskyUxX2ivq4+pJ7ALwbzwF55dZvy/23BrHAfvDVj7mg ";
string PassKey = "lLAHwegN8zdS7mIZyZZj+EmzlkUXkvEYxLvgAYjuBVtU8sw6wKXy2g ";
string rptlogin = ConfigurationManager.AppSettings.Get("rptlogin");
string rptPassword = ConfigurationManager.AppSettings.Get("rptPassword");
MemoryStream oStream;
CertificateOfEmployment rpt = new CertificateOfEmployment();
rpt.Refresh();
rpt.SetDatabaseLogon(rptlogin, rptPassword);
rpt.SetParameterValue(0, EmployeeId);
rpt.SetParameterValue(1, SigId);
rpt.SetParameterValue(2, SigPosition);
rpt.SetParameterValue(3, DateTime.Now);
oStream = (MemoryStream)rpt.ExportToStream(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat); --------- this gives me an error
// extract only the fielname
string filename = Convert.ToString((DateTime.Now.Month) + Convert.ToString(DateTime.Now.Day) + Convert.ToString(DateTime.Now.Year) + Convert.ToString(DateTime.Now.Hour) + Convert.ToString(DateTime.Now.Minute) + Convert.ToString(DateTime.Now.Second) + Convert.ToString(DateTime.Now.Millisecond)) + "BarangayClearance";
var len = oStream.Length;
// store the file inside ~/App_Data/uploads folder
// var path = Path.Combine(Server.MapPath("~/Content/Images"), fileName);
// file.SaveAs(path);
FileTransferServiceClient client2 = new FileTransferServiceClient();
RemoteFileInfo rmi = new RemoteFileInfo();
DateTime dt = DateTime.Now;
// upload file using webservice
DownloadRequest dr = new DownloadRequest();
//web service method to upload a file and return the unique id of the newly uploaded file
string fId = client2.UploadFileGetId("", filename, len, PassKey, Userkey, oStream);
//Instantiate the object Img which is a table in the database server of the application
//Download file using web service;
//DownloadFile in Refence.cs has been edited to return a RemoteFileInfo Class
//before, the return type of DownloadFile method was a Stream type
JsonResult result = new JsonResult();
result.Data = new
{
fileId = fId,
filename = filename
};
rpt.Close();
rpt.Dispose();
var arr = oStream.ToArray();
oStream.Close();
oStream.Dispose();
result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
return result;
}