Please check the connection again.

PS/2 / RS232 controller:
The cable has 8 pins on the keyboard side and 6 on the computer side. The cable must be connected to the keyboard PS/2 port of the computer. This connector is usually violet.

USB controller:
The keyboard must be connected through the USB cable to any of computer's USB ports.

Can you see at least one of the LED lights or hear the beeper if you press multiple keys now?

YES

NO