Aura HD Kobo Aura HD Edition 2 - black screen, unresponsive

I was just reading, locked my screen and put the ereader down for a second. I noticed the light hadn't turned off after a few seconds so I looked at it and the screen was black. I pressed the power button and it just turned off completely, now the screen is black, it's not being detected by my computer, and I've tried soft and factory reset, neither of which worked. Battery was around 40% at the time, and I've charged it for a bit and had no success.
Any ideas what this is?