If the button light on your vape pen will not light most likely your vape pen is locked. To lock or unlock the pen, rapidly and repeatedly press the button (6 or more times) until the button light flahses.
If the light still does not work, chances are your pen suffered a pocket break. This is when the button base snaps off the battery base cuasing the wires to break. If this happens, immediately recycle the battery base following your local recycle laws. To avoid pocket breaks, always remove the skillet heater before placing the pen in your pocket.