There is one possible reason for it, GitHub pages isn't enabled. To solve this, Repo Settings -> Github Pages section -> Select the main branch. If it is already there, then wait for some time and refresh your site again.
how to fix 404 error in github.io in new repositories? I tried the new, public, changed mode, nothing helps. there is a python script in the repositories to collect information, maybe there are some restrictions on github for python scripts?
how to fix 404 error in github.io in new repositories?