Check that the keyboard and mouse are connected to the correct port. The ports appear identical, but have different functions.
Disconnect all extension cables and switchboxes connected between the keyboard and the computer. If the computer is connected to a monitor, mouse, and keyboard through a Keyboard-Video-Mouse (KVM) switch, or console selector switch, disconnect the switch and connect monitor, mouse, and keyboard directly to the computer. If this solves the issue, contact the switch manufacturer for support and compatibility on the switch. Some switches can have a firmware update applied for the most common fixes.
Check the keyboard PS/2 connector for bent, broken, or missing pins.
Verify that the keyboard works in the System Configuration Utility. If so, load the default settings. Then save the settings, and exit the utility.
If the keyboard works during the POST or in the System Configuration Utility, but not in the operating system, check software logs for device driver errors. Contact your software vendor for more support in configuring the I/O devices.
Verify that the keyboard port is working by testing another keyboard on the computer. If the replacement keyboard works, the other keyboard is defective.
Verify that the keyboard is working by testing the keyboard on another computer. If it does not work on a second computer, the keyboard is defective.
If the keyboard is an option, verify that the computer meets the minimum operating system and hardware requirements of the keyboard.
For Rapid Access Keyboards (RAK), ensure that the most current drivers are installed and functioning properly.