Battery Failure

Charging and leaving to rest may allow the battery to recover, but do not overcharge a flat battery. Little and often is the rule for recovery by allowing the battery to cool or it will not re-charge. The internal sensor tells the unit that it is full when it is not. Try putting in the freezer for about 15 mins and then attempt a re-charge. It is quite possible that the battery has failed and replacement is the only option. You would need to return it to Amazon for service unless you can dismantle it yourself.

As an addition I checked out Amazon and they sell replacement batteries and kits from other suppliers to facilitate dis-assembly are available so anything is possible if you look hard enough