Pointcloud Select Points in View (with in the section box)

Hi , I am trying to select the points from point cloud . I am trying use to use “Sastrugo” Package, but retuned null Value as in image. Is there alternative solution for select the point with in the section please help me.

I am trying create floor and topo surface from point cloud.

Point Cloud Points

Is it possible select points with in section box.
Usually its possible to select elements with in section box. .I tried bounding box contain method but no luck.

help me some or give some hint…