I've created 3D polylines (polylineZ) in ArcGIS Pro, making use of the first and last point of X, Y, Z coordinates. The following output is shown with an absolute height.

However, when I share it as a web scene, I could not see the same result in ArcGIS Online even I changed the feature into the 3D option. Points are the first points of the polyline for indication use. Points are able to demonstrate the 3D effect under the option of absolute height.

How can I show the polylines in ArcGIS Online with same effect as shown in ArcGIS Pro? Any comments are welcome!
Thanks
Matthew