New US safety regulations require that at least one cigarette must be present in the vehicle for the lighter to operate. :wink:
If both 12v sockets are otherwise working (e.g. they provide juice to a connected cell phone charger), don't worry about it. The lighters portions themselves may just be broken. I am a smoker and have gone through my fair share of those thingies... Also, some 12v accessory power outlets - on newer cars especially - may look like cigarette lighter sockets but they are not designed to accept those, they only work with phone chargers and similar devices. On my 2006 RRS for example, only the front socket inside the ashtray accepts the supplied cigarette lighter. The same lighter inserted in the rear seat or trunk accessory sockets behaves just like yours: It pops right out.