Is your keyboard responding on boot? If not, and it is working normally when you are actually in your OS, then you may need to check the USB legacy settings in your BIOS. This is usually enabled by default, so if it has been disabled you will need to reset the BIOS to its defaults (or use a PS/2 keyboard) to enable this option. If your keyboard has a USB-PS/2 adapter, use that. If not, then follow the instructions below.
Try removing and replacing the battery (small round CR2032 type). When doing so, leave it out for about 5 mins before replacing it. This should reset the BIOS to its defaults, so you will need to correct the time and date and also adjust any other settings that have been reset. Alternatively, use the motherboard jumper (see the manual for details).