Вот мой код:
FTPConnectionManager.Properties["ServerName"].SetValue(FTPConnectionManager, strFTPURL);
FTPConnectionManager.Properties["ServerUserName"].SetValue(FTPConnectionManager, strUserName);
FTPConnectionManager.Properties["ServerPassword"].SetValue(FTPConnectionManager, strPassword);
FtpClientConnection ftp = new FtpClientConnection(FTPConnectionManager.AcquireConnection(null));
ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072 | (SecurityProtocolType)768;
ftp.Connect();
ftp.SetWorkingDirectory(strFTPPendingPath);
ftp.GetListing(out folderNames, out fileNames);
//UnZipping FUnctionlity
ftp.Close();
И я получаю
Служба FTP (FTP07) 503 Неверная последовательность команд (AUTH SSL / TLS требуется до аутентификации)