Hello, Please try pressing and holding the power button on the Nook for 25 seconds (count them out), then wait a full minute without pressing/touching anything else for the unit to reboot. If this does not work then try those steps up to three times and let me know what happens.
If you need further assistance let me know. Please do not forget to click a POSITIVE RATING before you go- as it's how I am credited for my work. You can follow up at any time, at no additional cost.