Wondering if anyone can tell me what’s going on here. I don’t know what I did but when I rotate the model there seems to be some section plane that makes everything invisible on one side. Would like to know what’s going on before I move on.
This is the classic clipping plane. It hides everything behind the camera (and sometimes thing in front of it because reasons).
It appears you are in parallel projection mode, and far closer to the geometry than you expect. Try switching to perspective mode and see what happens. Likely what is now clipped will be behind you.
Yep, Fun with clipping plane.
Or, the other way Zoom Extents.