It means that this plate is not talking to the others! (I asked the engineer).
To reset it:
Can I make a suggestion. There could be a misconfiguration with the control board that needs to be reset.
Firstly switch off the appliance and disconnect from the mains.
Reconnect and Press and Hold the Minus key '-'
While holding the minus key press keys 1 through 4 in turn within 4 seconds. (1 is bottom right, 2 is top right, 3 is top left, 4 is bottom left) Each key press will give an audible beep. Each must beep only once!) If any beep more than once,you must start again. It could take several attempts.
Once done you should get a 'C' displayed for each ring element.
Now place a pan of water on one element. Press the Plus key '+' next to the element ring and wait for the 'C' to change to '-'.
Repeat that for each element and once complete the appliance will switch off.
Reconfiguration is now complete and you can use the appliance as normal.
You may have to try this a few times before you get it right so if you mess up start over again by switching off and unplugging the appliance.
Good Luck
Anne, September 2011