I assume you were able to push the code successfully to the repo.
Make sure the following things are in place:
1. Angular Cli Version should be 8+.
2. Repo should be public and not private - navigate to settings and change the repo to public.
3. Try the following command: ng deploy --repo=https://github.com/<userID>/<repoName> --base-href=https://<userID>.github.io/<repoName>/
In the settings page, you'll get the generated link.
Check the network tab to see if the bundles are being loaded successfully, else clear the cache once and try : ctrl + shift + R.