Bosch Exxcel Frost Free Fridge Freezer (KGU31124)?

This is a frost free fridge freezer. The fridge is still working and when we switch it off & on the freezer section starts to cool then stops. The light to say that the freezer is not warm enough stays on.

Can anyone help to say where or what the problem is. This appliance is three years old. We have switched the whole thing off for 12 hours, cleaned it, checked for any blockages (Only one place in the fridge) but it has made no difference.

Fridge is working fine. Freezer is not working at all. Any ideas or help would be much appreciated.

Thank you