Can't charge/power on Nook HD+

The device won't power on. The screen and status light show no indication of activity when pressing or holding the power button (or any button / pairwise combination of buttons for that matter). The Nook HD+ (model BNTV600) has been unused for at least six months. It would not power on, so I presumed that the battery was simply dead and left it plugged in overnight to charge but would still not power on the next day. I suspect that it is not charging. When initially connected to a charger the light shows green for three seconds and shows orange/amber for three seconds and then remains off (there is a brief flicker orange/amber -> green at the transition between colors). The device was functioning normally before storage. I've tried charging with two different Nook HD+ -> USB cables and two different USB AC adapters and the behavior is all the same. Is this device completely dead? Are there any tricks to get this thing to charge / power on?