When you press the reset button, does the LED start pulsing?
potz1000:
In the Device Manager, although another COM port is active and I can change it
You were supposed to change the port in the Arduino IDE's Tools > Port menu, not Device Manager.
potz1000:
Same result.
Do you get the "Caused by: jssc.SerialPortException: Port name - COM4; Method name - openPort(); Exception type - Port busy." error message, but with the bootloader's COM port instead of COM4?