Give up smoking.
Check inside the lighter socket, make sure it is clean. If you have a test light check for power to the centre terminal in the base of the skt. If there is power the element is stuffed, or your device you are plugging in may have a fault. If no power, then you will have to check the wires on the back of it.
only had van couple of months and tried plugging phone charger in last week and nothing, cig lighter did not also work. jiggled with the front of it and the lights around the cig lighter socket have now come on but the thing itself still not working. i need to get to the back and check the wires i think