What could be going wrong?
Try to select different source from "Select source" dropdown/combobox and save. Then change it again into gh-pages branch and don't forget to save.
This fix my head-banging-404-waiting-nothing-happening-after-hours-refreshing
GitHub Pages often take a few minutes to show up, especially on the first creation of the
gh-pages branch. From the default 404 page:
There isn't a GitHub Page hosted here, sorry.
Are you trying to publish one?
We'll send you an email when your page has been built. It may take up to ten minutes until your page is available.