One star too many
Expert technique
How do you rule out a tile when nothing else works?
Imagine a star on it and look at what it blocks. If that one star would leave some row, column or region without room for its own two stars, the tile cannot be a star.
This is a single look ahead, not a guess: you are proving a tile impossible, not hoping a star is right. Try it on tiles that sit between two tight regions, where one star takes space from both.