why is my ge refrigerator freezer not freezing

I have a GE refrigerator freezer, and recently it has stopped freezing. I have tried to troubleshoot the issue, but I am not sure what the problem is. I have checked the temperature settings and they are correct. I have also checked the condenser coils and they are clean. I have also checked the door seals and they are all in tact. I have also checked the fan and it is running properly. I am at a loss as to what the problem could be. Does anyone have any ideas as to why my refrigerator freezer is not freezing? Any help would be greatly appreciated.