When you turned it off before, how did you power down the pi? Did you use the inline power button in the power cable? If so, it’s possible that the card might have been corrupted. If you have a known good backup, I would try flashing that back to the card to see if it boots. I don’t know why the power supply includes a push button switch, as this is a known way to mess things up. It’s best to SSH in and use the command
sudo shutdown instead, or wire up a momentary switch to the GPIO that runs a script to execute that command.
However the fact that you say that not even the red light comes on leads me to believe there is a larger problem, and the board might indeed be dead. If you have a spare SD card lying around, try flashing NOOBS on it and see if that boots.