The most common cause of a fridge suddenly going on strike is simply a stuck defrost timer.
Check with any appliance parts shop to see if your fridge has a mechanical defrost timer and where it is located inside the fridge.
Basically, the reason why your side by side fridge doesn't need to be defrosted like the old fridges is because it defrosts itself. It has a timer that runs on electricity, and every 10 to 24 hours, this timer diverts electric power from the fan and compressor to the defrost heater. The defrost heater melts the frost off the evaporator coils. Once all the frost is off the evaporator coils, the temperature in the vicinity of the evaporator coils rises quickly, and the defrost thermostat shuts off power to the defrost heater to prevent damage to the plastic and styrofoam parts around the evaporator coil.
Then, the fridge just stays in a coma until the defrost cycle is over, and the defrost timer diverts electrical power back to the compressor and evaporator fan. At that time, the fridge regains conciousness, and starts cooling again.
The problem is that sometimes the defrost timer will stick in defrost mode, so the fridge appears to have stopped operating completely, and with no warning that it's going to stop.
If you can locate the defrost timer, then you should find a shaft sticking out of it somewhere. That shaft will be designed to be turned in one direction only with a screw driver. Turning that shaft forward will advance the defrost timer and put it back into operating mode. Turning the shaft backward can wreck the defrost timer.
I'd check with your local appliance parts shop and find out a) if your side-by-side has a defrost timer or if that job is done electronically on circuit boards. If you do have a defrost timer, it'd be the prime suspect in my view, and you should advance the timer shaft to see if the fridge comes back to life when you do. If it does, you simply need to replace the defrost timer.