Work through these in order — it is almost always the first one:
Check the wall switch. Half of venue outlets are on a light switch, and a switched-off outlet is the single most common cause.
Reseat the white cable at the booth end.
Reboot: hold the side button 10 seconds.
If all three fail, call (914) 825-5498. Do not start taking the shell apart.
Didn't solve it? Text (914) 825-5498. If it's your event night, lead with that — those go to the front of the queue.