I had exactly the same Problem. The documentation about the cliping box is very confusion, also not complete, i think.
If i remember right, you have to select the component, then go to the Scene Tab, then at the most right, there is a Button Clipping Box.
Also, the message only tells you there are to many tris to display, you can still export it and view it in another tool, like Meshlab. But such high res meshes are really no fun to work with. Try to reduce the tri count with pressing on “Simplyfy”. There you can specify a target tri count. In most cases going from 40 mio tris to 20 does not make a significant difference in quality and detail.
Pro Tip: Clicking and reading around the Help in RC while your reconstruction process is in progress is always a good idea:) Learned a lot.