Problems with ftp

Question

I have a website on ASP.NET Framework 4.8. It downloads images from the ftp server. During the test run of the project from a working computer, everything works as it should, i.e. everything is downloaded normally. But when I publish a project with the same data to the server, an ArgumentException error occurs. Below is the try block in which it occurs:

try
{
    FileManager FM = new FileManager();
    using (MemoryStream ms = new MemoryStream(
        FM.ReadFile("***link to ftp***/Documents/" + "TechStoreDocuments/" + FileName,
        Convert.ToInt64(DT.Rows[0]["FileSize"]), 1)))
        
    {
        Image img = Image.FromStream(ms);
        string path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Images\\TechStore", FileName);
        img.Save(path, ImageFormat.Jpeg);
    }
    return FileName;
}
catch
{
    return null;
}

If I catch an error in the ReadFile method, then "WebException: unable to connect to a remote server" pops up in the FtpWebResponse response = (FtpWebResponse)FTPClient line.GetResponse():

public byte[] ReadFile(string Path, Int64 FileSize, int FTPType)
{
    CurrentSpeed = 0;
    iTransData = 0;
    Position = 0;
    TotalFileSize = 0;
 
    Byte[] buffer = new Byte[2048];
 
    using (MemoryStream ms = new MemoryStream())
    {
        try
        {
            FtpWebRequest ftpClient = (FtpWebRequest)WebRequest.Create(Path);
 
            if (FTPType == 3)
                ftpClient.Credentials = new NetworkCredential(ServerFTP178Login, ServerFTP178Pass);
            if (FTPType == 2)
                ftpClient.Credentials = new NetworkCredential(LocalFTPLogin, LocalFTPPass);
            if (FTPType == 1)
                ftpClient.Credentials = new NetworkCredential(HostFTPLogin, HostFTPPass);
            if (FTPType == 0)
                ftpClient.Credentials = new NetworkCredential(ServerFTPLogin, ServerFTPPass);
 
            ftpClient.UseBinary = true;
            ftpClient.KeepAlive = true;
 
            TotalFileSize = FileSize;
 
            ftpClient.Method = WebRequestMethods.Ftp.DownloadFile;
            FtpWebResponse response = (FtpWebResponse)ftpClient.GetResponse();
 
            //write file
            Stream responseStream = response.GetResponseStream();
 
            int bytesRead = responseStream.Read(buffer, 0, buffer.Length);
            Position += bytesRead;
 
            if (bytesRead > 0)
                ms.Write(buffer, 0, bytesRead);
 
            while (bytesRead > 0)
            {
                if (bStopTransfer)
                {
                    bStopTransfer = false;
                    ftpClient.Abort();
                    response.Close();
                    responseStream.Close();
                    break;
                }
 
                bytesRead = responseStream.Read(buffer, 0, buffer.Length);
                if (bytesRead > 0)
                    ms.Write(buffer, 0, bytesRead);
                Position += bytesRead;
            }
 
            Position = TotalFileSize;
            ftpClient.Abort();
            response.Close();
            responseStream.Close();
            ms.Capacity = (int)ms.Length;
 
            return ms.ToArray();
        }
        catch (Exception ex)
        {
            bStopTransfer = false;
            GC.Collect();
            return ms.ToArray();
        }
    }
}