The model number is RSB195BSSB
Invalid model. Do you mean RB195BSSB?
If so, the first thing I would check is if the freezer evap fan is running when the compressor is running. If the compressor is off you can put it into "forced mode" by pressing "power freeze" (might be called "super freeze") and "fridge" buttons simultaneously for 8-12 seconds until the display beeps and goes blank. After this, press the freezer button one time and the compressor kicks on.
(to exit later... just unplug or re-enter forced mode and press the freezer button 4 times)
Now both evap fans should be turning with the doors shut. To trick the unit into thinking that the door is shut you need to press the door switch. Within 30 seconds (of course, holding it in place) you should feel cold air being blown by the fan.
If no, then you probably have ice buildup blocking the air (defrost problem) or you have some loose wiring to the fan. Remove the evap cover and take apart the fan cover and check the connector. I have seen these come loose many times... easy fix. Note on these DC fans... they RARELY fail, but you can test with a 9v battery if in question.
If you have ice buildup you need to check the defrost heater and thermistor, The heater should be about 60Ω and the thermistor should have continuity.
If no ice buildup and fans look ok.. check the frost patterm. If it is ok.. even across the coils, then you probably have a main pcb issue.