1.) Go to the physics tab and choose the lowest possible physics available. If some parts are too small, they will be highlighted in red in the preview window and won't upload.
OR
2.) Change the LOD to: Lowest = Zero, Low = Zero, Medium = Use LoD from above.
OR
3.) Use a physics cube, select "Choose from file" and navigate to the cube.
Physics cube link:
OR
2.) Change the LOD to: Lowest = Zero, Low = Zero, Medium = Use LoD from above.
OR
3.) Use a physics cube, select "Choose from file" and navigate to the cube.
Physics cube link:
[To see links please register here]