Was it like that out of the box, or did it randomly stop working?
My headphones had the same issue (they'd show the purple light while plugged in, while otherwise being completely lifeless), but it was resolved when I plugged it in to my computer via the USB-SPI programmer and reset the chip with it. Maybe it's just, you know, stuck.
If you don't have the programmer handy, unplugging the battery seems to be a good general workaround for firmware crashes like this one, depending on the device, but I wouldn't recommend that as I don't know if the battery is even removable. Could be soldered to the motherboard.
Hope things work out for you. It's a very nice headset
-odd