Failed - network error when downloading excel file made by EPPlus.dll

Try this:

using (ExcelPackage p = new ExcelPackage())
{
    //Code to fill Excel file with data.


    Byte[] bin = p.GetAsByteArray();

    Response.ClearHeaders();
    Response.ClearContent();
    Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", Nombre_Del_Libro + ".xlsx"));
    Response.BinaryWrite(bin);
    Response.Flush();
    Response.End();
}   

I prefer not use response.End() because throw an exception

    protected void DownloadFile(FileInfo downloadFile, string downloadFilename, string downloadContentType)
    {
        Byte[] bin = File.ReadAllBytes(downloadFile.FullName); 

        Response.ClearHeaders();
        Response.ClearContent();
        Response.ContentType = downloadContentType;
        Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", downloadFilename ));
        Response.BinaryWrite(bin);
        Response.Flush();
        Response.SuppressContent = true; 
    }

I had the same problem when I was using Response.Clear() and Response.Close() and had to avoid them to look my code as below which is working.

Response.Buffer = true;
Response.ContentType = mimeType;
Response.AddHeader("Content-Disposition", "attachment; filename=" + nameOfFile);
Response.BinaryWrite(bytes);
Response.End();