Using the Simple Sudoku Puzzle Solver I reached the following scenario in two rows of a puzzle :

RowX [7][8][1] [349][3469][2] [ 369][349][5]

RowY [4][139][5] [8][1239][39] [7][6][12]

In rowX I identified a probable hidden triple [3,4 and 9] in columns 4,5 and 8 which would thus eliminate candidate 6 from column 5 leaving number 6 as the only remaining candidate in column 7. According to the Puzzle Solver this move was accepted as valid..

For rowY I again assumed that a hidden triple [1,3 and 9] occurred in columns 2,5 and 6 which would eliminate candidate 2 from column5 and thus leave number 2 as the only remaining candidate for column9. However, the Puzzle Solver rejected this move.

I would appreciate any explanation as to why this is so. I hope I'm correct in not needing to show the whole puzzle to illustrate my dilemma. Any comments explaining this scenario would be appreciated.

Regards Bonsai Cec