Wait for the update
It may take up to 10 minutes for updates to be reflected on the GitHub pages web site.
GitHub Pages
MakeCode uses GitHub Pages to convert your repository into a full web site!
The pages web site will either show the rendered README.md file; or the compiled game running in full screen for Arcade.
Custom pages
By default, MakeCode overrides the supporting files to render the pages project in each release. You can disable this behavior by adding this code in pxt.json:
disableTargetTemplateFiles: true