Zanussi ZUF105W not freezing properly

Wanted some advice? Bought this freezer second hand. Worked fine the first few weeks but the past 2 weeks its stopped freezing properly. Its still cold inside but food, such as ice cream, doesnt freeze properly. Theres a button with an orange light to quick freeze but once pressed, after say an hour, the red warning light comes on and it beeps. Any one have any idea how i can fix it or what the problem is? Theres no build up of ice and we did leave it to stand for 24hrs after moving it, thankyou.