First, you should make sure it's not just frozen; press the reset button just in case.
There's also a possibility that your charger/cable are simply bad and it was not charging. You can always try just about any other 5V power supply with a USB connection to make sure.
Since it otherwise, seems to be completely dead, and I'm guessing you have at least moderate electronics skills, you can open the Paladin and cut the battery wires (which you have to do anyway for replacing it) and then connect a 5V regulated DC supply directly to it. (Disconnect any USB chargers, if present.)