Parameters are not being passed to stored Procedure

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ASP

I have an export page that I am trying to use to download a file created on the fly to the user. In the main page I use a record set to store data returned from a SQL Stored procedure and then dump the contents into a Grid.
I then want to allow the user to save the grid contents as a text file tab delimited. So i redirect them to another page and call the same SQL stored procedure to populate the recordset and write it to a file as a download.
The problem is the parameters (using the exact same code that works on the other page) are not being passed to SQL so my record set comes back empty. If I place default values in the SP the record set is returned and the file is created and downloaded.

set connUBC3=Server.CreateObject("ADODB.Connection") 
        connUBC3.Open  "UBC"	
	    If Err.number <> 0 then
		    TrapError Err.source & ": " & Err.description
	    End If
	
	    set cmdTranByCardNo = Server.CreateObject("ADODB.Command")	
		    set cmdTranByCardNo.ActiveConnection = connUBC3
		    cmdTranByCardNo.CommandText = "Transaction_GetByMerchantIdAndCardNo"
		    cmdTranByCardNo.CommandType = adCmdStoredProc
		    cmdTranByCardNo.Parameters.Add("@MerchantID", SqlDbType.nvarchar)
		    cmdTranByCardNo.Parameters("@MerchantID").Value = vMID

            cmdTranByCardNo.Parameters.Add("@CardNo", SqlDbType.nvarchar)
			cmdTranByCardNo.Parameters("@CardNo").Value = vCardNoString
				'Process results


            set SearchTranByCardNoRS = cmdTranByCardNo.Execute ' @MerchantID = vmid,@CardNo = vcardnostring	
           
            dim icount2 
            icount2 = SearchTranByCardNoRS.RecordCount	
		    If Err.number <> 0 then
			    TrapError Err.source & ": " & Err.description
		    End If

            SearchTranByCardNoRS.MoveFirst        
            if  not SearchTranByCardNoRS.eof then

                headertext = "attachment;filename=GiftTransByDate-" & vMID & fileExt
                Response.AddHeader "Content-Disposition",headertext

                Response.Write "TRANS DATE" & sCh & "TERMINAL NUMBER" & sCh & "LOCATION NAME" & sCh & "CARD NUMBER" & sCh & "TRANS  TYPE" & sCh & "TRANS AMOUNT" & sCh & "REMAINING BALANCE" & sCh & "AUTHORIZATION" & vbCrLf
                SearchTranByDateRS.MoveFirst
                do until SearchTranByCardNoRS.eof
                    Response.Write SearchTranByCardNoRS("TranDate") & sCh & SearchTranByCardNoRS("TerminalID") & sCh & SearchTranByCardNoRS("LocationName") & sCh & SearchTranByCardNoRS("CardNumber") & sCh &  SearchTranByCardNoRS("TranType") & sCh & SearchTranByCardNoRS("TranAmount") & sCh & SearchTranByCardNoRS("RemainingBal") & sCh & SearchTranByCardNoRS("AuthCode") & vbCrLf                          
                    SearchTranByCardNoRS.Movenext
                Loop
                SearchTranByCardNoRS.close
                SearchTranByCardNoRS = nothing
            End if

So why does the exact same lookup work in one page and not the other?
I have the same problem with multiple Stored Procedures where they all work on one page but not this one?

Thanks