FAQ 22.5 - My mob won't do anything when I force it. How do I tell what's happening?
Try using the 'snoop' command to see what exactly is going on. A lot of stupid stuff can prevent a mob from completing its actions, including not being strong enough to wield a weapon, not being able to move because it's surrounded by nomob rooms, etc. Just snoop it and try the force again, you should see why the mob isn't reacting.