The power connection is faulty or the unit isn't getting power.
Check the power cord and outlet first. Grasp the plug itself, not the cord, and ensure it's fully inserted into a 120V AC outlet. Make sure the outlet works by plugging in another device. Inspect the cord for any damage, bending, or pinching. Do not use if the cord or plug is damaged.
If that didn't work: The unit may have been moved while running. Unplug it, wait 30 seconds, then plug it back in and press the Power Button.
Heads up: Always hold the handle on the back to move the unit. Never pull it by the front panel or the power cord.