Check their status page [1] to see the progress:
> Investigating - We are currently investigating 403 / 429 errors received by some users.
> Investigating - We are currently investigating 403 / 429 errors received by some users.
> Monitoring - Our content delivery partner has informed us they've implemented a fix. We are monitoring. Feb 17, 13:07 UTC
Edit: And in the OP GH thread, people are also mentioning it's back up.