@davidfor, thanks your kindly help.
If you shutdown the device, the cover wouldn't help. That is only used to wake the device from sleep.
Actually current screen always display "power off", I try to press power key by several ways, short press, long press(5s, 10s, 20s, 30s) to blink different light. But no response from kobo.
Plug it in and charge it for an hour or then try again. Otherwise, you will probably need to do a factory reset. See
https://wiki.mobileread.com/wiki/Kob...Aura_Edition_2 for how to do this.
I should charge it more than one hour and follow this guide to do factory reset. But unforuntly I can see the red-green light blink, but screen doesn't display recovery or restore something like that.
Any other more suggestion or hints?
Many thanks.
Br
Gen