For me none of the restart approaches helped. The ad was still displayed on the screen, the display light did not go on, nothing happened. The one and only thing that worked for me was to put on the USB cable and charging the device, which I did all night. Hint: The power LED to the side of the connector must turn on while charging, if not, you may have a bad cable.
After having the device charged, I still couldn’t turn it on. So I tried all the restart possibilities described (push the button for 7s, 40s, 45s, 60s). All the descriptions tell to unplug the device before restarting it. After nothing worked I connected it to a power source (my laptop) again and pushed the button for a long time again and after letting it go the display light went on and the ad changed to the battery symbol with the “!” mark on it.
I think now it’s charging.