To Reset your Series 3 desk
1. To reset the system, press and hold the “Up” and “Down” buttons at the same time. The unit will then emit a single ‘beep’ and the display will show “rsT“ and the desk will start moving downward into the
lowest position. Never release the buttons until the unit emits a second single ‘beep’.
2. The desk will then move upward a little and the display will show the current desk height.
3. The reset process is now finished.
See the full instructions here.
Or watch the video: