Kontena Pharos CLI Toolchain will use SSH access for making connections to cluster machines. For this purpose, all machines in a cluster must be configured to allow an user with passwordless sudo permission.
echo "$USER ALL=(ALL) NOPASSWD:ALL" | sudo tee /etc/sudoers.d/$USER
Please ensure the host operating system you are using is configured accordingly.
Most likely a master host is missing private_address or private_interface. Reason for the error message is that address is behind NAT and cannot be used for etcd cluster communication.