Select a different Key Photo for a Face in People

I have tried to do this by opening all the faces for a person, clicking "Faces" in the upper right corner of the screen, selecting a preferred photo/face, and then clicking the share button in the upper right corner of the screen. Searching the internet, one search said that a share alternative would be "Make Key Photo", however this option does not come up. I also selected the preferred photo and under Images, I tried select "Make Key Photo", but this selection is greyed out. The only way I could change the face was by making a preferred face a favorite (in its lower left corner), and then delete the photo that was the current Key Photo. Not a good option.

What am I doing wrong?