BrainFlow cannot access port in OpenBCI Cyton Daisy

Hi,
Could anyone give me a hand ? I have this issue in UNITY.
I am using BrainFlow.

Thanks for your help!

        public class Sphere : MonoBehaviour
        {
            private BoardShim board_shim = null;
            private MLModel concentration = null;
            private int sampling_rate = 0;
            private int[] eeg_channels = null;
            private double[,] unprocessed_data = null;
            private int board_id;

            // Start is called before the first frame update
            void Start()
            {
                BoardShim.enable_dev_board_logger();

                BrainFlowInputParams input_params = new BrainFlowInputParams();
                board_id = (int)BoardIds.CYTON_DAISY_BOARD;
                input_params.serial_port = "COM3";

                board_shim = new BoardShim(board_id, input_params);
                board_shim.prepare_session();
                // board_shim.start_stream (); // use this for default options
                board_shim.start_stream(450000, "file://file_stream.csv:w");
                System.Threading.Thread.Sleep(5000);

            }

            // Update is called once per frame
            void Update()
            {
                BrainFlowInputParams input_params = new BrainFlowInputParams();
                input_params.serial_port = "COM3";
                unprocessed_data = board_shim.get_current_board_data(20);
                eeg_channels = BoardShim.get_eeg_channels(board_id);

                foreach (var index in eeg_channels)
                    Debug.Log(string.Join(", ", unprocessed_data.GetRow(index)));
            }
        }