Flatten: Lock+radius doesn't work. Please help

I was using the flatten tool and turned on the “Lock + radius”. I tried to drag the radius but the radius seemed to be constrained in a really small size.

Any idea? Thank you in advance!!

Isn’t that because the surface of the sphere isn’t wide enough? Try other primitives or other shapes.

Thank you so much for the hint.

Even though not the problem of shape or primitive, I tried to increase the area sampling radius and it works as I want now!

Thank you!