@kirth
On my wife's kobo this kind of thing often happens, it's frozen off and nothing can wake up, neither the power button nor the reset pin hole.
The only solution is to be patient, try and retry the reset pin (during half an hour genarally), keeping the reset pin pressed for 2 or 3 seconds each time, again and again until magically it decides to power on.
@tshering and @kirth
And if your problem was the same of mine, KSM is not involved since her Kobo (H2O) is "pure"
Anyway, glad to read that everything's ok for you now