This Sudoku is not valid

Some potential values that are part of the solution are missing in some empty cells. But the Sudoku has a solution if the missing potential values are ignored.

This probably means that you have manually removed a potential value that was part of the solution. Note that the Sudoku Explainer takes care of every manually removed potential value.

Choose the menu Tools -> Reset potential values to automatically re-compute all potential values of all empty cells. Then you can try again solving this Sudoku.