Some sites do not allow requesting the same file twice (IDM)

Some sites do not allow requesting the same file twice :

I face the previous error when i try to download my pdf in button click event:

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 private void AddReportToResponse(LocalReport report )
        {
            string mimeType;
            string encoding;
            string extension;
            string[] streams = new string[100];
            Warning[] warnings = new Warning[100];
            Response.Clear();
            byte[] pdfStream = report.Render("PDF", "", out mimeType, out encoding, out extension, out streams, out warnings);

            Response.ContentType = mimeType;
            Response.AddHeader("content-disposition", "attachment; filename=Application." + extension);
            Response.BinaryWrite(pdfStream);
            Response.End();

        }