If the freezer needed defrosting a few weeks ago and its done the same again then its going to be a defrost issue on this. As its not defrosting itself so the ice builds up and after a few weeks it stops the airflow so you get this issue.
If you are looking at fixing this yourself then you need to unplug the appliance and empty the freezer.
then you need to remove the side rails on the bottom half of the freezer then you can remove the back panel in there.
Once this is off check to see if its covered in ice.
If so then use a hairdryer and melt all the ice in there.
Once clear you will see the defrost heater under there and the 2 black wires going up the side to the top.
With a test meter you need to check the heater and see if faulty.
If so then the heater will need to be replaced.
But if the heater is fine then it will be the main control board at the back thats the fault here.
So try that if you can as if its all iced up again then its going to be either the defrost heater itself or the control board thats casuing this fault.
But if you dont fancy doing this and want to get it working for the time being then do a 24 hour defrost on it and leave the freezer door open and that will at least get it working again for a bit. But you will find in say 3 weeks it will happen again.
If you need anymore info just get back to me.