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 hob. The area surrounding the hob must not be too dark.
Take any cookware off the hob and wipe away any residues.
Check that there is nothing covering the entire hob unit or the sensor controls.
Disconnect the power supply to the hob for approx. 1 minute.
If the problem persists after the power supply has been restored, please contact the Customer Service Department.