2 arduino connected to USB

I have 2 Arduino cards connected to USB, it is COM5 and COM6. 2 days ago they both can be seen by Arduino IDE and were listed in device manager. I can communicate with both of them. Today, only one can be seen by Arduino IDE but the device manager still can see COM5 and COM6 are used by Arduino cards. Both cards' lights are on.

But only one card can communicate with COM port.

What is the problem?

Thanks

First try to futher isolate the symptom.

Swap the two arduino boards. Does the problem move with the board or stay with the physical USB port?

Go with the board. The light is on. The COM port name does not change.

I uninstall and reinstall the driver fix the problem. But now the port name change to COM6 and COM7 seems COM5 is not working. Can we rename the COM port

In the advanced tab, it shows COM3, COM4 and COM5 are in use. But no hardware is using those ports.