Diagnosis
Probably not the whole box. The handset connector—that thin, phone-style cable running from the control box to the keypad—is notoriously flimsy and often gets pinched during assembly or wiggles loose.
How to Fix It
Unplug the desk from the wall. Trace the thin, rectangular cable from the back of the keypad down to where it plugs into the main control box (usually mounted under the desk near a leg). Unplug it and firmly re-seat it. While you're there, check the cable for any obvious kinks or cuts. Plug the desk back in.
If That Didn't Work
The keypad itself might have failed. You can order a replacement handset directly from FEZIBO; it's a plug-and-play swap. The control box itself failing is much rarer.
Heads Up
Don't try to use generic RJ11 phone cable as a replacement. The pinout is often proprietary. You need the specific FEZIBO cable.