I can't help with the unicorn extension, other than to suggest double-checking that you installed the current version, and that it's installed correctly.
But I could walk you through the basics of using the Gcodetools extensions. Also I could check your SVG file for possible problems.
Since you see the same problem with both, for me, that would point to something about the drawing which the extensions don't like. Maybe something isn't converted to a path, but which the other programs you tried, accepted anyway? But there are too many things to try and guess beyond that. So looking at your file would be the best way.