Can you hear the compressor at the back running still?
Also has the freezer fully defrosted?
Ok what you need to do if you can is pull the appliance out and remove the metal cover on the back at the bottom.
Behind there you will see the compressor (black pot).
Feel this and see if its hot to touch. If it is then the compressor is the fault and will need to be replaced. Now this isnt a diy fix so a fridge engineer will need to do the work as it involves regassing the appliance.
But if the compressor is cold and not running at all then its possibley the control board at the top of the appliance at fault as it may not be sending the power down to the compressor for it to start up and run.
So check them if you can as if its not running then its one of the above thats the fault here.
If you need anymore info just get back to me.