Serial monitor window opens frozen My serial monitor window opens frozen, without any output or possibility to input, or even activate the window.
Sketch is very simple, but behavior is same even with empty sketch, so I assume problem is not in sketch. I also checked if sketch is uploaded correctly by uploading simple sketch with blinking diode, which worked.
Same behavior with Arduino Nano and Uno.
I tried to reinstall IDE, uninstalled, removed and reinstalled serial driver (ch340) with no success.
I can see Serial monitor window only on windows taskbar, it won't activate after click.
Until now I haven't had any significant problems with IDE or serial monitor for years.
Try updating the java. Also check whether the device manager shows the USB serial port without any yellow warning sign on it.
If there is a current short in the usb port that specific port will be off for safety, restarting the computer should resolve that problem.