SerialPort in c# winform

Hello there !
I am try a very simple to read serialport of OPTA

using System;
using System.IO.Ports;
using System.Windows.Forms;
using System.Windows.Forms.DataVisualization.Charting;

namespace OptaStudy2
  {
  public partial class Main : Form
	{

	public Main()
	  {
	  InitializeComponent();
	  serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);
	  }

	private void BtnConnect_Click(object sender, EventArgs e)
	  {
	  if (!serialPort1.IsOpen)
		{
		serialPort1.BaudRate = 9600;
		serialPort1.PortName = "COM4";  // As per your setup, make sure it's the correct COM port
		serialPort1.Parity = Parity.None;
		serialPort1.DataBits = 8;
		serialPort1.StopBits = StopBits.One;
		serialPort1.NewLine = "\r\n";  // Arduino println sends \r\n for new line
		try
		  {
		  serialPort1.Open();
		  BtnConnect.Text = "Disconnect";
		  }
		catch (Exception ex)
		  {
		  MessageBox.Show("Error opening port: " + ex.Message);
		  }
		}
	  else
		{
		serialPort1.Close();
		BtnConnect.Text = "Connect";
		}
	  }


	private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
	  {
	  try
		{
		string data = serialPort1.ReadExisting();
		richTextBox1.Invoke(new MethodInvoker(delegate
		  {
			richTextBox1.Text += data;
			}));
		}
	  catch (Exception ex)
		{
		// Log or display the error message
		MessageBox.Show("Failed to read from serial port: " + ex.Message);
		}
	  }

	private void Main_Load(object sender, EventArgs e)
	  {
	
	  }
	}
  }

and in my IDE

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println("Test message");
  delay(1000);
}

i am using OPTA Finnder AFX000002 ,
this code is work very well with arduino uno, but OPTA is not
is there any different uno vs OPTA here ?

i found the solution that OPTA work with SerialUSB , not Serial as normal arduino Board !

What did you have to change in your C# code to get it to work ?