A few times when my Nook HD+ has been completely shut down it would initially fail to turn back on for a while. It seems that it will not boot up until charged to about 65%. Once it gets back to around 65% it goes on and works fine.
I could see it failing to boot up if the battery is extremely low, but it seems that it shouldn't take this much of a charge to turn back on. Is this normal behavior for the Nook HD+, or is there a problem with mine?
Having to wait until 65% is not normal. Mine usually boots back up again at about 15% but needs more to stay up once it boots. I'm thinking either the battery is shot or there are apps being loaded upon boot that are requiring a lot of time and juice. (that last bit is a guess on my part)
If no one else comes up with a better idea that has a solution you can use, you might want to call CS about a replacement device or take it into a store if there is one near you. The store is the preferred way to do it, but not everyone has one near enough to use. I've had to have devices replaced before, they are usually pretty prompt about getting it to you and you get to keep your device until the replacement arrives.
Take it into a store.
It's a strange bug. It might mean the batter level indicator is gone, or it might mean the battery is failing. How long have you had it?
How long does the battery last?