Hotpoint XEX95 T1| GZ Fridge Freezer

The fridge works as it should, change temperature setting or put Super Cool function on it does what it is supposed to do. The freezer gets no colder than minus 10 and doesn’t change temperature whatever setting you change. I have turned the appliance off for 48 hours to see if had frozen water and that was the issue but no water appeared anywhere including the tubing on the back of the appliance going to the compressor. The fridge / freezer has been back on now for over twenty four hours and fridge is around 3 to 4 degrees and the freezer is minus 10. The appliance is around four years old. What part could be causing the issue? Any help gratefully received. Thanks Ian