Diagnosis
The dock's sensors aren't detecting the clean water tank, usually due to a misaligned tank, debris on the contacts, or a faulty float sensor inside the tank.
How to Fix It
Remove and reseat the tank firmly. Take out both the clean and dirty water tanks. Check the clean tank's bottom for the metal contact pins—wipe them and the corresponding slots in the dock with a dry cloth. Reinsert the tank until you hear a definitive click.
If That Didn't Work
Inspect the tank's internal float sensor (the white plastic piece that moves up and down). Gently move it to ensure it's not stuck. Try filling the tank to only 80% capacity, as an overfilled tank can sometimes jam the float.
Heads Up
This error will prevent any mopping or auto-refill functions. If reseating doesn't fix it, you likely need a replacement clean water tank—contact support with your dock serial number.