CFS2 is a tad different if you're used to CFS1. It also depends which keyboard layout you're using.
Combat Keyboard ..... Backspace to toggle (select) ordnance. Enter to fire.
FS/CFS1 keyboard ..... Shift + 3 to toggle & 3 to fire. (main keyboard not num keys)
You might like to read my CFS2 FAQ page.
http://www.simviation.com/lair/cfs2faq.htm