Subtract appears to not work?

This is in Glyphs Mini 2, version 2.1.4. I am trying to knock out one circle from another.

I have the shapes selected per the attached screenshot. When I click the “subtract” icon in the Transform panel, the direction of the selected path reverses and the path deselects, but it does not apply the subtraction.

you don’t use subtract for that. It is explained in this tutorial: Drawing Good Paths | Glyphs (scroll down to “Path Orientation and Order”)

I’m clearly missing something obvious, then! With the paths drawn as attached, it’s not subtracting, but that appears to be what the tutorial calls for.

Is it possible that there are two path on top of each other (the bigger circle)?

That was it! Thank you so much.