I tried to open an .obj file from Maya in substance painter, but got an error message saying "[Scene 3D] Unable to open file ".../.obj". I tried with a .fbx file and got the same error.
Once thing I noticed, when selecting Template, I used to choose the option "PBR - Metallic Roughness (allegorithmic)", but the current version doesn't have that option any more. The one I selected (screen capture below) didn't work. I also tried a few other options but with no luck. I don't know if this was the reason I couldn't open the .obj/.fbx file.
And where can I look up the detailed information on all the options of the Template dropdown?
The template doesn't change the way we import 3D meshes. There is likely an issue with the content of the mesh. Please post here the full error message (visible in the log window) when you import the object.