new samsung note 8 and suddenly black out and unable to switch on and off
Welcome to AndroidCentral
Sorry to hear your Note 8 isn't working. What were you doing with the phone before it suddenly turned off?
Have you dropped it at all? Or has there been any screen damage since you purchased it?
I would say, put the phone on charge for 2 hours and then see if it boots up. You can also try plugging the phone into your laptop or computer via USb and see if the laptop registers the phone.
Hope this helps.