generates error The data is invalid. (Exception from HRESULT: 0x8007000D)

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C#

sir,
bellow is my code for send fax.but its generates error The data is invalid. (Exception from HRESULT: 0x8007000D).
please help me if any one knows the answer

public void SendFax(string DocumentName, string FileName, string RecipientName, string FaxNumber)
       {
           if (FaxNumber != "")
           {
               try
               {
                   FAXCOMLib.FaxServer faxServer = new FAXCOMLib.FaxServer();
                       faxServer.Connect(Environment.MachineName);


                   FAXCOMLib.FaxDoc faxDoc = (FAXCOMLib.FaxDoc)faxServer.CreateDocument(FileName);

                   faxDoc.RecipientName = RecipientName;
                   faxDoc.FaxNumber = FaxNumber;

                   faxDoc.DisplayName = DocumentName;


                   int res = faxDoc.Send();

                   Label1.Text = res.ToString();
                   faxServer.Disconnect();

               }
               catch (Exception Ex) { throw (Ex); }
           }
       }

       protected void Button1_Click(object sender, EventArgs e)
       {
           SendFax(txtdocname.Text,Server.MapPath("~/"+FileUpload1.FileName),txtrecipentname.Text, txtfax.Text);
       }