Calendar Mac OS X “Failed to authenticate with Google”Posted: August 2, 2016
You are trying to set up your Mac OS X Calendar to work with your Google account. You know it is possible, because you have done it before, but this time it just does not work. Everything seems to be correct, but whatever you do, you keep getting the message:
Failed to authenticate with Google
One special reason for this may be that if you are using some kind of a personal firewall, e.g. TCPBlock, it is blocking attempts of the Calendar application to reach the Google server.
Try to disable the firewall for a short while and see if Calendar begins to work as it should. If it does, adjust your firewall settings.