Observed issue: While trying to login into a Windows system with Duo 2FA enabled and using local logon credentials, the following error was displayed.
There was an error communicating with the duo authentication server 12007
Observed cause: This error occurs when the device cannot reach Duo cloud to perform secondary authentication and the user is not yet enrolled for offline mode.
Solution: Ensure that the device has connectivity to the Internet and can communicate with Duo cloud over TCP/443. Furthermore, ensure that the user is enrolled to use offline passcodes.
Further reading: https://docs.microsoft.com/en-US/windows/win32/wininet/wininet-errors