Siemens induction hob flashing 'G / 9?

good morning, my Siemens induction hob, which i have had since brand new, two yeras ago has stooped working.

When i place a pan on the hob and turn the temperature up dispalys, an upside down 'g' then a '9' flash, any ideas? I couldnt see anything in the user manual to explain!

on the top left corner it says, 'schott ceran' and '9000780929'

any help is appreciated.

thank you