Safety first: Unplug before cleaning or descaling.

Follow manual reset: Consult the user manual for the exact button combination to reset the descale indicator (often holding the clean/descale button for several seconds).
Run full descale: Ensure you completed a full descale cycle from start to finish without interruption.
Rinse cycles: Run at least two full reservoirs of fresh water to ensure the flow sensor registers normal operation.
Power cycle: Unplug for 10 minutes, then plug back in and attempt the reset again. If the icon remains, the control board may have a firmware issue.

The display shows a descaling or clean icon and will not clear after cleaning.

Possible Causes