If you see this error when trying to sign in using GitHub for Mac, it means that your company is not on the latest release of GitHub Enterprise.
With the release of two-factor authentication on GitHub.com, we also shipped a new major release of GitHub Enterprise that supports 2FA. However, this change is not backwards compatible with older releases of GitHub Enterprise.
If your operations team is unable to upgrade to the latest release of Enterprise, please contact GitHub support and we can help you out further.
