Thanks, Denman for your reply and sorry for taking that long to reply with more info; had to deal with some other critical issues.
It is only the "fridge part" that is not cooling the juices, food, etc. The ice-maker/freezer works normally, and the compressor, fans all are okay. I checked the compressor, it is vibrating as normal. Since I replaced the old thermostat with a new one, could it be something else that causes the fridge not to work, maybe the "defrost Timer?