The Theme Demo on the Themes Site is missing its CSS resources because the generated Permalink is wrong.
I have notified the theme author on GitHub
There are special requirements for Theme Demos to work and sometimes when a theme is updated with new features the Demo can break.
I’m a bit surprised this wasn’t caught sooner but currently there is another issue with many Theme Demos throwing a 404 on the website and @digitalcraftsman is investigating .
Thank you for reporting the broken demo.
In the future if you catch another broken theme demo on the Themes Site please notify the theme’s author directly on the theme’s repository.
@lucperkins See the GitHub issue I opened in your repo. There is a fix for this problem.