Diagnosis
No power to the control box. The issue is either the power supply brick, the cable from the brick to the desk, or the internal fuse in the control box.
How to Fix It
First, check the 24V DC power adapter brick. Look for a green LED. No light means a dead power supply. Next, trace the thin 2-pin cable from the brick to the control box. Ensure it's fully seated at both ends.
If That Didn't Work
The control box has an internal 5A fuse. You must open the control box housing to check it. Unplug everything first. A blown fuse indicates a short, often from a pinched motor cable.
Heads Up
Do not use a third-party power adapter. The voltage must be exactly 24V DC and the amperage must match or exceed the original. Using the wrong adapter can fry the control board.