In case it’s relevant to your situation: If the Y/N column already had a value (e.g., “N”) in each row in the data source, then revising the column’s App formula expression won’t affect those existing values. Rather, the revised App formula expression will only apply to a given when it’s invoked for that row–e.g., when the row is edited, thus triggering recalculation of its columns.
In the expression test mode, the values displayed for each column may be the inputs to the expression evaluation (i.e., not the outputs), and an empty Y/N column resolves to false for purposes of various functions. I suggest confirm what value ends up in your actual data when using the app.