Check if you can hear if the evaporator fan is running.
The fan drags air across the freezing cold evaporator unit in the freezer compartment and it is directed to the refrigerator section and the freezer section to cool them down to the set temperatures
The evaporator unit and fan is in the freezer compartment behind a panel.
The fan will run as long as the doors are closed and the compressor is running. When you open a door the fan will stop. You may have to place an ear against the fridge cabinet to hear it stopping and starting when you open and close a door (either door).
Do not confuse this fan with the condenser fan which is outside the compartments near the compressor and condenser and can run whether the doors are open or not
If you can’t hear the evaporator fan at all then it may be faulty or it may be iced up.
If it is iced up there may be a problem with the auto defrost in the refrigerator.
The freezer will stay cold because that is where the evaporator unit is located but the fridge will get warm if there is a problem with the auto defrost which affects the evaporator fan
This could be caused by a faulty:
defrost heater - not working so all the ice is not melted and over time this builds up and the fan is iced up.
thermostat - which tells the control board to turn the compressor back on when the temp reaches 0 deg C (32 F) so as to not damage the evaporator unit.
thermistor - which tells the control board what the actual temp is
drain tube - which directs the meltwater out of the freezer. If it is blocked then the meltwater can’t drain and the ice forms again causing a build up etc.
control board - which controls the operation of the fridge.
Auto defrost occurs once every 8-12 hours (depending on manufacturer) and lasts for about 20-30 minutes. The compressor is stopped and the temperature in the freezer is allowed to rise to 0 deg C (32 F) to melt any ice formed on the evaporator unit. The meltwater then drains away to the evaporator pan below the fridge where it evaporates. The process is sped up by turning on the defrost heater as you don’t want the frozen food to start to thaw.
If the auto defrost appears to be working OK it could be a sticking damper unit preventing air getting into the refrigerator section to cool it down
As an aside, never raise the bottom of the fridge at the front more than enough to allow the doors to self close from the half open position. This will ensure that the doors are always shut and that the evaporator fan can operate to cool the fridge/freezer.
Apologies for the long answer but it may help if you know how it works so that you can determine what is not working