I am Brazilian, and there are weeks that I have been trying to install Anki on my Lenovo Ideapad 3i notebook, the site doesn’t load and it just shows this message.
We’ve seen this a couple times – where certain Brazilian ISPs are blocking access to GitHub. Unfortunately there’s little we can do about it.
Figuring out a different internet connection or using a VPN are probably your options. You can search the internet for other suggestions – https://www.google.com/search?q=brazil+internet+access+to+github.