While my update was downloading, I checked an old file and put it into Simplify3D and it was correct (on all 3 axes). I will restart Fusion now and try it again...
OK, it was the same after the update.
Now this was an old finished model I have printed many times. You may want to verify your axis setup and see if it changed. By my defaults, +X goes right in both fusion and Simplify3D.
EDIT: I didn't make it clear above, I loaded an old finished model but did a fresh .STL export (twice). Both files load the same way into Simplify3D, and that orientation matches how they are seen in Fusion. I suspect the answer you need is not in the file export utility, but in your setup somewhere.
