In my case - In storyboard i had a two labels as in image below, both labels was having desired width values been set before i made it equal. once you unselect, it will change to automatic, and as usual having below things should work like charm.
1.rowHeight = UITableView.automaticDimension, and
2.estimatedRowHeight = 100(In my case).
3.make sure label number of lines is zero.