I had the same problem, the fridge section was warm and not cooling but the freezer section worked and kept our stuff frozen. We had a repairman take a look and after four trips, he finally fixed it. He explained that new refrigerators have become a little more sophisticated which is good in some ways and also bad. New fridges come with a two part evap system instead of the old which was all in one. There’s an evap line for the fridge and one for the freezer and a motherboard controls them. In my case, the fridge evap part was not opening. The repair guy brought a new part and swapped them out. FYI, the part has copper connections so welding is involved in the repair. Once swapped out, he plugged in the fridge waited 24 hours and it worked. One more thing, the part in question will sort of look like an octopus with three copper arms in case you want to diy. I hope this helps.
-Lee