Can't reduce row height - tried everything!

Naomi,

You probably have a text label at the top of a task bar (subtask) that isn't being displayed. If this happens on just one bar, the Gantt chart will appear more vertically extended, as shown in your image.

Out of curiosity, look at the Gantt with all the subtasks displayed: (Select the entire project = Click the top left corner of the table > Menu ribbon > View > Data > Outline > All Subtasks), and check if any task shows a value at the top of the bar. If so, double-click the bar and Reset it to remove it.

More automatically and safely, as John points out: Menu ribbon > Gantt Chart Format > Bar Styles > Format > Bar > Bar Text > Reset  (N.- Now with all tasks and subtasks previously displayed).

Remember that if you accept save on exit, the changes will be saved in all subprojects (deleting bar text on individual tasks).

We look forward to your results.

Ignacio