Hi Patrick @TK5EP
I tested your pcb file and configuration and this is working for me in KiCad nightly Win10-64, FC 01.6 and 0.17 latest ...
I opened the .kicad_pcb file with a text editor and I noticed that at line 310 you have:
(at (xyz 0 0 0))
(scale (xyz 1 1 1))
(rotate (xyz 0 0 0))
and following your alternate prefix:
prefix3D_2 = C:\Portable datas\Datas KICAD\modules\packages3d\
I placed a model named:
in the alternate folder. Then I have this path existing:
C:\Portable datas\Datas KICAD\modules\packages3d\BG115-05-xx.STEP
After that, launching KSU everything worked as expected, building up the 3D mechanical STEP model of the board, collecting STEP models from the first configured path and the last from the alternate path.
Do you have the same configuration and have you placed your STEP file(s) in the secondary folder?
from your previous post about the displayed error message:
it seems you have 'TK5EP.3dshapes' in the searched string...
may be your alternate path is this?
C:\Portable datas\Datas KICAD\modules\packages3d\TK5EP.3dshapes
and not the one in the ksu-config.ini config file.