If you are using the B&N charger socket and still having this issue, I would take it into a B&N store and get them to take a look at it. They may be able to help.
Otherwise the only thing I can think of is the dreaded de/re register.
I hope you get it sorted.
Does it show the battery sign with a lightning bolt or just a blank battery with a little red on the edge?
The lightning bolt means it's charging but doesn't have enough energy to turn back on yet. The blank battery means that it doesn't think it's plugged in and isn't charging (but has just the eensie-weensiest bit of battery left for that one thing).
So, if it's the lightning bolt, give it time (up to half an hour) and see what it says? If it's the blank battery, sounds like something in the device itself is the problem, since you already replaced the cord, at which point definitely take it in.