Create system break issue

In Engrave mode, Shift-S works to create a System Break.
In Engrave mode in the Formatting panel, clicking ‘Create System
Break’ in the Format Systems section does nothing, however.

Did you have something selected in the music already?

Yes, I had the same note selected when I tried each way of creating a system break. Shift-S worked immediately. The staff split and the screen displayed the System Break indicator.