I have a rooted nook that would not power up (stuck on last display screen). When I'd plug it in -- it showed a GREEN light (already charged). I tried all of the reset fixes (20 seconds hold, 1 min hold, wait a minute, 15 secs) -- nothing worked.
Finally, I pulled it apart using this tutorial on Youtube:
[Can't post link because I'm a newbie --- just search for "How to Take Apart a Nook Simple Touch"]
Very easy to do if you have a T-6 torx driver. I unhooked the battery. Held down the power button (white button if disassembled) for about 30 seconds to discharge the board. Then hooked the battery back up, reassembled, plugged in -- and it started charging (orange light).
It looks like the issue was -- the nook was registering the battery as fully charged -- and it was completed depleted. The above fix seemed to reset it.
Hope that helps someone.