Netlifycms login with Github said page not found

Hi all,

I just integrated netlifycms to my site.
When I access /admin and click Login with Github,
it redirect to /auth?provider=github&site_id=xxxxxx&scope=repo but the page is not found.

What else am I missing?
Any suggestions are welcome.

Do you have any redirects in place that are a little bit too aggressive maybe?

I believe there are no redirect rules set.
I use create-react-app and I didn’t use react-router.

Could you share your site name?

I changed the from github to git-gateway, regenerate the token and now works.