My computer-device manager-ports (COME and LPT)-check which COM port your device occupies, and then pay attention to opening the device when you open the COM port of the computer, so that the COM port will be ok.

For example, your instrument occupies COM2. If you open COM 1 on your computer, you can't connect to COM2, so you can't connect to the instrument. You must open COM2 on your computer to connect to the instrument.