Error while uploading .hex file to Arduino Nano using ArduinoUploader in .NET C#

I'm using a Arduino nano and am trying to upload a .hex file to the Arduino using the ArduinoUploader Package through a .net C# interface. And I run into the error:

Unable to aqcuire sync in SendWithSyncRetry for request of type ArduinoUploader.BootloaderProgrammers.Protocols.STK500v1.Messages.ReadSignatureRequest!

Code:

static SerialPort _serialPort = null!;

static void ResetArduino(string portName)
{
    _serialPort = new SerialPort(portName, 1200);
    using (_serialPort)
    {
        _serialPort.Open();
        _serialPort.Close();
    }
    System.Threading.Thread.Sleep(5000);
}

static void Main(string[] args)
{
    try
    {
        ResetArduino("COM8");
        var uploader = new ArduinoSketchUploader(
            new ArduinoSketchUploaderOptions()
            {
                FileName = @"PATH_TO_HEX",
                PortName = "COM8",
                ArduinoModel = ArduinoModel.NanoR3
            });

        uploader.UploadSketch();
    }
    catch (ArduinoUploaderException ex)
    {
        Console.WriteLine($"Error: {ex.Message}");
    }
}