✅ Error: The remote server returned an error: (403)

using System;
using System.Data;

public class Program
{
    public static void Main(string[] args)
    {
        try
        {
            string filename = "";
            string sharepointUrl = "";
            string sheetName = "";
            string connectionString = "";
            string tableName = "";
            string username = "";
            string password = "";

            Console.WriteLine("Lade Datei von SharePoint herunter");
            SharePointDownloader.DownloadFile(sharepointUrl, filename, username, password);

            Console.WriteLine("Lese Excel-Datei herunter");
            DataTable dataTable = ExcelReader.ReadExcelFile(filename, sheetName);

            dataTable.Columns.Add("Dateiname", typeof(string));
            foreach (DataRow row in dataTable.Rows)
            {
                row["Dateiname"] = filename;
            }

            Console.WriteLine("Importiere Daten in die SQL-Datenbank");
            SqlImporter.ImportToSqlDatabase(dataTable, connectionString, tableName);

            Console.WriteLine("Führe gespeicherte Prozedur aus");
            SqlImporter.ExecuteStoredProcedure(connectionString, "sp_async_SP_starter_Trigger", "Import VKS Strom", "ABRECHNUNG", "sp_zev_upsertNBK", filename);

            Console.WriteLine("Daten erfolgreich in die SQL-Datenbank importiert");
        }
        catch (Exception ex)
        {
            Console.WriteLine("Fehler: " + ex.Message);
        }
        finally
        {
            Console.WriteLine("Drücken Sie eine beliebige Taste, um das Programm zu beenden");
            Console.ReadKey();
        }
    }
}