|Seven generic possibilities for keyboard failure at startup::|
1) The keyboard or its cable is bad.
2) The keyboard bios on the motherboard is bad.
3) On most motherboards there is a small inline fuse near the keyboard connector. Perhaps that's blown. You can't tell by looking at it. It looks like a axial resisor or capacitor. It'll be labeled on the motherboard as F1, F2, etc. but always starting with F.
4) If you have a lock/unlock keyed switch on the front of the computer it is locked or the keyboard lock pins on the motherboard have been jumpered.
5) The motherboard KB connection is loose or bad.
6) Make sure it's not a keyboard designed for the IBM PC/XT and compatibles (8088's). Those used different timing signals than 286's and above.
7) It's plugged into the wrong port.