This has apparently been an issue for over a year, and I'm somewhat disappointed that for a $150 piece of software, it still hasn't been fixed.
Whenever you import an STL through the GUI menus, Simplify3D comes back with an error "CANNOT AUTO ARRANGE. LARGEST PART EXCEEDS BUILD DIMENSIONS". After that, the program locks up and you have to force quit. However, if you drag the STL file into the window, the model imports perfectly fine. This is a mild annoyance, but I keep a MacBook hooked to my printer almost constantly. I'll lock up the program, potentially losing whatever I was working on, and have to restart. Again, it feels unacceptable for such an expensive piece of software. Is there any update on this issue?