DIAGNOSIS This usually means the keypad is in 'lock' mode, a feature meant to prevent accidental changes to memory presets (great for offices with kids). The basic functions still work, but the programming buttons are disabled.
FIX You need to unlock the keypad. To do this, press and hold the 'M' button for about 10 seconds. You should hear a long beep, and the display might flash. That's it. Now try pressing 'M' and then a number button to set a memory height—it should work. If it doesn't, repeat the process, holding the 'M' button a full 10 seconds.
IF THAT DIDN'T WORK If the buttons are still dead, there could be a fault in that section of the keypad's membrane or a problem with the data wire in the cable. Check the small rectangular 4-pin connector where the keypad plugs into the control box under the desk. Unplug it, inspect for debris or bent pins, and reconnect it firmly.
HEADS UP The lock function can sometimes be activated by accident if you lean on the panel or press multiple buttons during startup. If you share the desk, teach others how to unlock it, or just leave it unlocked if you don't need the child-proofing.