E4418B Serial with C# project

private void send_Click(object sender, EventArgs e)
{
    try
    {
        byte[] data = Encoding.UTF8.GetBytes(demo_textbox.Text + "\n");

        serialPort1.Write(data, 0, data.Length);
    }
        catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }
}

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above one is my C# code for send command

it works on "*IDN?" and "RST" and some else

but It never works on query commands

What should i do first

Do i need to chage mode? about like remote mode?

Or change SCPI? but SCPI mode doesnt work with "*IDN?"

.. Regards