When you are done charging, you should press the “stop” button in the charger cubby. If the connector is still locked after having pushed the button (or if you have stopped charging from within your vehicle), then the vehicle charge port lock is still engaged; this is often a feature designed to prevent others from unplugging your vehicle. This can usually be resolved by locking & unlocking the car doors with the car keys – once the car doors are unlocked again, then you should be able to remove the plug.