I’m a beginner. I have done something to my model that isolates it. New added meshes in the viewport disappear when in front of the model. Checked layers. All on same layer and I can see the new mesh until it passes in front of the older work (the model).
BTW: LOVE this course! So helpful!

No such problem with my trigger. The cube does not disappear when it passes in front.
Thanks for any ideas how I got my model in such a state.