I tested the Linux version and it opened all files correctly. I don't have a Mac at hand but will try to help. Does the same file open on Windows? What exactly is the error message? Which Molflow version is it?
Is there a file that is non confidential and you can upload here that reproduces the error? Are you sure that the STL is exported in ASCII (as opposed to binary) format?
Are you sure the file is really STL, and not let's say STL.txt with hidden extension?
I'm downloading the file you attached and test it on different computers with fresh Molflow installs and regardless of the operating system it opens. If you're on Mac, can you preview the STL file with space in Finder?
If someone is coming here later: these issues were likely caused by the operating systems’s locale defining , (comma) as decimal separator instead of . (dot)
Molflow follows the regional settings, but STL files are probably not.
In Windows, you can change the separator:
Windows Control Panel | Region and Language | Formats | Additional settings…
We are checking if we can force US locale (with . decimal) in future versions.