As this is a frost free appliance the fridge section gets its cooling from the freezer. The fan in the freezer blows the cold air into the fridge section.
If you hear the fan catch something then its possibley a build up of ice inside the freezer has jammed it up.
Now there 2 things you can do for this. Either empty the freezer section and remove the rear panel in there.
There you will see the evaporator and fan unit. If this is blocked with ice use a hair dryer and fully defrost the freezer section as this will clear the air ways and allow the air to flow up to the fridge section. Then retry it and fingers crossed this will sort it.
But if you don't want to go removing panels then you need to do a full defrost on it.
Empty it an turn it off for 24 hours and leave the freezer door open. This will allow the ice in there to melt away. Then turn back on and see how it goes.
If you need anymore info just get back to me.
I have defrosted it by taking the panel off. should the fan be on when the power goes back on?
the condenser bit is back on, when does the fan unit start going?
The fan usually starts when the compressor does. Sometimes you cannot hear it as the doors are closed but just listen very carefully at the freezer door and open very slightliy and see if you can hear the fan.