Tap it with a hammer in a few spots.
Why? The charger is 100% solid state.
To the OP: Read the manual that came with the charger. It's possible that the conditioning cycle will take quite a few hours. (For many chargers, a conditioning cycle isn't something done every time it charges. It keeps count of charge cycles, inserting a conditioning cycle based on factory-set profiles. This count can be maintained even though the charger is unplugged frequently.) Your manual may indicate it's not really stuck - if you let it run the course of an expected cycle.