Hotpoint FFA64 fridge freezer high temp light on

Hi. The high temp light has been on for 12 hours after a few days of being on and off.
There is a frost forming on the back wall of the fridge section but only on the top third of the wall.
The freezer compartment is not freezing. I have taken off the back panel in the freezer compartment and it was not iced up.
I have now had the fast freeze function on, and the temperature dial for the freezer compartment turned up from 3 to 5 (highest setting) for about 1 hour.
The fan is in the freezer compartment is not spinning.
The appliance has not been moved.
Can any one give advice on what they think has gone wrong?
Many thanks,
Nigel.