Clean the connector, the plug with a high-volume spirit that does not leave residue. Use q-tips. If that does not help, *gently* bend the cable at the base of the plug to check if it's not broken - that's the most common spot where cables break. It'd also be useful to check whether there's any current at all going through the charger - you can use a tool or... well, you're tongue - it's only a few volts, it'll barely sting. If the charger is dead, it's dead and it needs to be replaced. If you still have warranty on the system, return it.