ceramic hob is locked - how do I free it please?

for some reason my ceramic hob has 4 flashing 'L' signs - I assume it has locked - as I have recently moved to this property I do not have a make or instructions - the glass plate says Schott Ceran - there are 2 large burners & 2 small - the touch controls are in the middle bottom - usually light up with a dot on the one that has the pan/saucepan on