PeteB wrote:If the people who designed the board tell you there is a regulator and you need 6V or more, I would believe them. 5V probably results in sending a low voltage to the Pi, so it may work, but not well.
Which LED is flashing? The one in the button, the red one on the edge of the Pi board?
I do not think that the button can possibly work without some software, like the shutdown script for example.
If you have a voltmeter, you can check the voltage on the Pi, but I can only conclude that if you use a 5V supply, the voltage at the Pi will be too low to work correctly.
I mentioned, my psu is 7.5V and LED of the power button is flashing. I have linked my youtube video