If you use GitHub page you may encounter “Page build failure” issue. You should then have a look to GitHub documentation to solve your troubleshooting. By the way, if you don’t find a proper answer to your problem, don’t forget to try to build your Jekyll page locally in production environment!!! Basically, most Jekyll users use it locally in development environment (or in “local” mode). However, some pages in _layout or in _include should have the following snippet:
{% if jekyll.environment == "production" %}
<<for production environment only contents>>
{% endif %}But, as on GitHub page the build environment is set to production, you don’t see the errors related to the <<for production environment only contents>>!!! So, before pushing your modification on GitHub page, try first check-in them in production environment to be sure that all the contents have been tested properly!