This error occurs when Home Assistant is unable to communicate with our authentication server. We have been able to identify two different reasons for this issue to appear.
Pi-Hole will block the connection under certain configurations. Try temporarily disabling Pi-Hole to see if you are able to estbalish a connection.
The second reason the issue can occur is if Docker is misconfigured. This issue is especially common for people using the
GENERIC installation of Hass.io on top of Ubuntu Bionic or another Linux installation. It is related to IPv6
being incorrectly marked as available.
The solution is to make sure that Docker uses a public available DNS server, like the Google ones. As root, run:
mkdir -p /etc/docker
echo '{"dns": ["8.8.8.8", "8.8.4.4"]}' > /etc/docker/daemon.json