Try another cable and charger. The NT will charge slowly with a regular micro-USB cable so long as you use a high output charger of about 2.1 A. Expect it to charge at about 10% per hour. If that works, your charger and/or cable may be bad. Hopefully, that's the extent your problem.
My Nook tablet use to charge up fine whether it was on or off but now it only charges when the power is off. I don't know whats causing my issue but I thought this idea could work for you.