download meshlab. It's free.
Just loading into meshlab and resaving the STL can fix most problems.
How many faces do you have? Meshlab tells you at the bottom of the main window.
If it's more than say 1 million or even 100K it's worthwhile to reduce this with meshlab. Google something like "meshlab reduce number of faces" or "triangles" or something similar as the feature is well hidden.
Does anything recognize it as an STL file? Try meshlab, perhaps? It sounds like there's some fundamental file format problem, rather than anything about particular settings for how the mesh is toleranced.
Link to post
Share on other sites