GitHub suffered a global system outage, preventing access to the site, issuing commits, cloning projects, or performing pull requests.
The reason for the outage has not yet been determined, but the GitHub status page says only that it has investigated the deterioration in performance for GitHub Actions, Codespaces, Issues, and Pull Requests.
By 2:30 PM EST, the outage had been fixed and GitHub resumed normal operations.
For more information, read the original story in BleepingComputer.