There are lots of reasons for it not to cool but I think the first thing to check in your case is the (drum roll):
'''Start Relay'''
The start relay works in conjunction with the start winding to start the compressor. If the start relay is defective, the compressor may sometimes fail to run or may not run at all. As a result, the refrigerator will not be cold enough. To determine if the start relay is defective, use a multimeter to test it for continuity between the run and start terminal sockets. If the start relay does not have continuity between the run and start terminal sockets, replace it. In addition, if the start relay has a burnt odor, replace it.
It’s a cheap part if that doesn’t do it we can go into the multiple other possibilities.