Macbook Pro has the "keyboard illumination keys" F5 and F6.
For some reason, there is a small "no entry" sign whenever I hit those keys.
The keyboard's illumination doesn't seem to change at all, how do we fix this problem?
The laptop makes note of ambient lighting and disables keyboard backlight when it's not dark. This is similar to the automatic display brightness system. Both are there to save power.
Your keyboard backlight should work in a dark room or if you cover your iSight camera so the laptop thinks it's dark.