Zanussi frost free fridge freezer, fridge not working.

Zanussi ZX99/5SI about four years old. Fridge not working and warning lights on. Had problem with same symptoms about 18 months ago and the probe set was replaced. This seemed to do the trick until now.
The fridge is warm and the freezer has ice in the duct pipe(at the top left hand side) and a build up of snow around the ‘fins’ in the top of the freezer compartment.
I have previously posted the problem but I’m getting a bit desperate and would really appreciate help with this.

Many thanks