Diagnosis
The desk's controller is getting conflicting signals from its safety sensors. This is almost always the anti-collision system triggering.
How to Fix It
Clear the obstruction. First, remove everything from the desk surface. Next, check under the desk for anything touching the legs or feet. Then, manually lift the desk from the bottom of the frame a few inches and press the up button. This often resets it.
If That Didn't Work
The cable connecting the control panel to the motor might be pinched. Unplug the desk. Check where the cable runs from the control box up into the column. Make sure it's not caught between metal parts.
Heads Up
Never try to force the desk to move while it's beeping. You can damage the motors or the controller. Always unplug it before checking cables.