I just created a footprint for a new part but when I try to use the STEP file provided by the manufacturer, nothing appears in the 3D Models Preview section, nor in the 3D Viewer.
I’m able to view the .stp file in Fusion 360 without any issue so I think the file is fine. I’m also able to view 3D models for other parts in the default KiCad libraries without issue so I think my install is fine.
To make the patch work, you have to delete files in the 3d cache. This is an obscure KiCad “feature” hidden in Users-Yourname-AppData-Local-kicad-5.99-3d