Gen 2 Keypad

My gen 2 key pad has illuminated to battery light to indicate that it requires recharging - this will be the first time since its' installation about 7 months ago. I remove it from it wall holder and plug it into a mains charger using the orange coloured lead that it came with and nothing happens, despite leaving it on-charge over night it is still displaying the low battery light and the app also confirms that the battery is low. I have tried other leads too to no effect. Am I doing something wrong, or is the unit faulty?