ICP issues with open3d (ZED 2i camera)

I wrote this code for the registration of two point clouds.

I experienced some issues: the open3d function for importing the PLY file I acquired using the ZED Depth Viewer didn’t work. It worked with other PLY files but it didn’t work with those I obtained from the ZED Depth Viewer. That’s why I used the pyvista library for importing the files.
Then, in order to give a proper argument to the open3d ICP function I used these instructions to obtain a point cloud variable which could be accepted as an argument.

My problem now is that I observed a quality loss after this conversion.

Could someone please support me and help with this issue? Thank you in advance.