The problem is that if I plug the scanner into the USB port then the keyboard never appears.
Using IME not miss out, although the icon appears on the taskbar.
This scanner is USB type, and works as a keyboard.
No need to install any driver, it works perfectly.
I've tried several similar, all USB.
What can I do to show the virtual keyboard when needed?
The scanner doesn't have to work as a keyboard. Turn off keyboard wedge emulation mode and turn on simple com port emulation. Then use the USB serial library to read the input from the scanner. You will find all the bar codes to do this in the reference guide.