I was just setting up my P4P+ for a morning shoot and I must have touched the sleep button on top of the built-in display. The screen is now dead and won't turn back on. Any clues? The manual says to hold the button down to restart but this isn't working.

I was just setting up my P4P+ for a morning shoot and I must have touched the sleep button on top of the built-in display. The screen is now dead and won't turn back on. Any clues? The manual says to hold the button down to restart but this isn't working.