Point in curve error

Hello, I am new in Grasshopper, and I have a doubt regarding the point in curve component, because when the input is a circle, the component works fine, but when I plug in the same curves in the input P, it won t work. In theory, the input should be a point, and I am pluging a curve, but why in the first attachement the component works and in the second attachement not?

Thank you!