Troubleshooting I can't start the descaling procedure of my SENSEO. Find out below how to get the descaling process of your SENSEO started. Calc-Clean tool is in place If the Calc-Clean tool is not in place, the CALC light flashes quickly to indicate that the tool is missing. Remove the milk container unit from the machine and place the Calc-Clean tool in the coffee spout. Now your machine is ready for descaling. SENSEO has heated up Wait until the light ring around the on/off button stops flashing slowly and lights up continuously.