I'm having an issue with control points in Clip Studio Paint.

To try and be specific, tonight when using the operation tool, usually when I highlight an object such as a figure line or shape, I see control points that I can change to whatever I may want it to be.

For some reason now, I can neither see those control points, nor use them. I tried looking through a User Guide but I've found no real answer.

So I guess what I'm asking is, how do I make the control points visible/usable again? What did I do wrong?