The sensitivity level of the sensor controls has changed.
Make sure that there is no direct light (from the sun or from an artificial source) falling onto the cooktop. The area surrounding the cooktop must not be too dark.
Take any cookware off the cooktop and wipe away any food deposits.
Check that there is nothing covering any part of the sensor controls or cooktop.
Disconnect the power supply to the cooktop for approx. 1 minute.
If the problem persists after the power supply has been restored, please contact Miele Service.