It's a pretty good setup actually.... just one compressor and evaporator plate instead of two. When you only need a fridge, just use the freezer as a fridge and switch the fridge section thermostat off.
I'd check that the power cables are plugged in, then switch that thermostat to max. Mine has a fuse about 6in from where the power leads connect to the compressor control board fan output terminals. Fan could be bad, they are pretty cheap...