DIAGNOSIS: The handset's memory has been corrupted or cleared. This often happens after a power flicker or if the batteries died completely.
FIX: You need to reprogram the memory positions. 1) Move the desk to your desired height using the up/down arrows. 2) Press and hold the "M" button. While holding it, press the number (1, 2, or 3) you want to assign. Hold both for about 3 seconds until you hear a confirmation beep. 3) The LED next to that number will light up solid, indicating it's saved. Repeat for each preset.
IF THAT DIDN'T WORK: The handset itself might be failing. First, try replacing the AAA batteries with fresh ones, even if the display works. Weak batteries can cause memory circuits to fail. If new batteries don't fix it, perform a full controller reset. Unplug the desk from the wall for 60 seconds, then plug it back in. Immediately try reprogramming the memories again.
HEADS UP: The memory function requires constant, low-level power from the control box to retain settings. If you plan to unplug the desk or move it for a long time, write your height settings down first, as they'll likely be lost.