USB keyboard number pad not working when plugged into Inspiron 11 3000 series lap top.

I have attached several different USB keyboards (including Dell SK-8135) to my laptop to use the number pad in my accounting soft ware. None of the number pads work. I have checked that these keyboards work  when attached to my desktop, they do. I have checked to insure the num lock is on. It is. I tried searching for a driver specific to the Sk-8135 keyboard. No Luck. Any help is Greatly Appreciated.

Julisa