I get this error with S3D 4.1.2 "Failed to Locate G-Code File for Conversion" . It will not generate a .gcode file for BFB. I use a lot of post processing commands that operate on the .gcode file before it gets converted to .bfb.
In the scripts I have output file format set to .bfb.
This did not happen with S3D 4.0. Although they seemed to have cleaned up some issues with the .bfb conversion in 4.1.2, I need it to process the G-Code file as an interim step as there are details lost if they only output the BFB and many of my "Additional terminal commands for post processing" do not work.