When I try to add a face the circle appears but I can't move or expand it. What happened? This worked last week.

When I add a new photo and it fails to recognize a face and I try to add a face the circle appears, with both the X and the expansion spot, but I can neither expand or move the circle. It opens a small version of the photo I'm working on and then closes it as soon as I release the mouse button. The ability to change the circle size worked just a week ago and now does not. How do I get that capability back?