Diagnosis
This is almost always a memory lockout. The desk thinks it's at its programmed minimum or maximum height and is refusing to move to prevent damage.
How to Fix It
You need to reset the desk's memory. 1) Hold down the down arrow button for 10 seconds until you hear a long beep. 2) Immediately after the beep, press and hold the down arrow again. The desk will now descend to its absolute lowest point, resetting that limit. 3) Let it go all the way down until it stops. Now use the up arrow to raise it to your desired height. The memory should be cleared and it'll move normally.
If That Didn't Work
If it still just beeps and won't budge, check that the control box under the desk is firmly connected. Unplug the desk from the wall, then firmly push in the rectangular connector from the hand control into the control box. Plug it back in and try the reset sequence again.
Heads Up
After a reset, you'll need to reprogram any height presets by holding the M button and then a number button at your desired height.