Is the freezer still working?
If so then open the freezer door and you will see a vent at the top. Shine a tourch in there and see if theres a lot of ice or frost in there and let me know.
the freezer is working and there is no ice in or on the vent
Ok if the freezer is working but there no ice in vent then its either a faulty fan motor or the fan is blocked with ice due to a blocked drain hole.
As with this being a frost free appliance the fridge gets its cooling from the freezer. The fan in there blows the cold air into the fridge section.
What you need to do is empty the freezer and turn the appliance off for 24 hours and leave the freezer door open. This will allow the ice to melt in the evaporator housing unit.
Then retry it and see how it goes. Fingers crossed this will cure it. But if it doesn't and the freezer gets cold again but the fridge isn't then its probberly a faulty fan motor in the freezer that will need to be replaced as these can fail on these.
But try the defrost first as say about 7 times out of 10 its this rather then the fan.
But if after say 3 weeks it does it again then you need to pull the appliance out and loom at the back of the appliance and you will see the compressor. Going into the drip tray on the top is the drain hose. Push a screwdriver into the end to remove the rubber bung as this likes to stick and stops the water draining. If this is the case you will see the water coming out from there.
Then that should cure it.
If you need anymore info just get back to me.