Check to see if you are getting power to the bulbs when depressing pedal. If
not, check power into and out of the switch. A burned out switch is not
uncommon.
To replace the switch, pull the switch body back towards the steering wheel.
You will hear a ratcheting noise. reach around the front side of the switch
and squeeze the tabs. (It will be very useful if you have a new switch to
look at, before removing the old one)
Snap the new switch into place, being careful to notice it is keyed to go in
a certain way. Connect the plug.  Depress the brake pedal and push the
switch all the way in until it bottoms out. Release the break pedal to set
the switch to it's correct position.