Hello and thank you for the question.
Could you provide more details:
1. What windows are you using?
2. What's the firmware version of your device?
Possible solutions to help you solve the problem:
1. Have you tried unplugging and replugging the device?
2. Have you tried first solution (1.) after restarting the device?
3. Have you tried to restart your PC?
4. If none of these solutions help:
- Navigate to "Device Manager"
- Find "STMicroelectronics Virtual COM Port (COM 3)"
- Right-click it, select "Port Settings" tab
- Click "Advanced"
- Change port number (to any other number below 10) and click OK.
Please let us know if you solved the problem
Best regards,
Support team