my replacement plug in keyboard will not control volume

How can I make my replacement usb keyboard adjust volume? In keyboard preferences I have selected 'use all f1,f2 etc keys as standard function keys' and in keyboard shortcuts I deselected (disabled?) f10 - application windows, f11 desktop, f12 dashboard shortcuts, and allowed full keyboard access all controls. Previous keyboard instantly controlled voilume using f10, f11 and f12 - no adjustments necessary.