DIAGNOSIS The descale reminder is timer-based, not sensor-based. It activates after approximately 80-100 brew cycles. The reset procedure must be followed exactly, or the light will remain illuminated.
FIX With the unit plugged in and OFF, press and HOLD the CLEAN button for 5 full seconds. The 'DESCALE' light should flash and then turn off. If it doesn't, unplug the unit, wait 60 seconds, plug it back in, and immediately try the 5-second CLEAN button hold again.
IF THAT DIDN'T WORK The membrane switch behind the CLEAN button on the control panel may be faulty or the connection to the main board is compromised. The switch itself is part of a sealed control panel.
HEADS UP The descale light is a reminder only. You can still brew coffee with it on, but scale buildup will reduce heating efficiency and eventually cause overheating or failure. Use only vinegar or citric acid solution for cleaning; do not use harsh descalers.