I tried to reset it with minus + power several times, but no amount of attempts to recharge, either with the given charger or any other have been able to get the LED charging light to work.

I used in once, when I bought it in May ... kept it plugged in to keep a good charge ... triend using it in July, but wouldn't stay powered up .... plugged it back in again to make sure it had a charge ..... tried it again today, in September, and it would stay powered-up -- kept shutting off