Many times I’ve tripped over this, you’ve got to be careful when using triple backticks, Kramdown Markdown will try to auto-detect the programming language for syntax highlighting, but if it fails, your GitHub pages will fail to build. Sidestep the problem entirely by specifying the programming language explicitly at the beginning of the three backticks. See a list of supported syntax highlighters here.
20200227/https://stackoverflow.com/questions/11568093/syntax-highlighting-on-githubs-wiki-specifying-the-programming-language
20200227/https://pygments.org/docs/lexers/