I am configuring Kubernetes cluster with 2 nodes in coreos as described in https://coreos.com/kubernetes/docs/latest/getting-started.html without flannel. Both
Please see this as a reference and maybe help you resolve your issue by exporting your certs:
kops export kubecfg "your cluster-name" export KOPS_STATE_STORE=s3://"paste your S3 store"
Hope that will help.