I was trying to deploy prometheus-kubernetes. After I ran ./deploy,

Deploying Prometheus Operator
serviceaccount "prometheus-operator" configured
clusterrole "prometheus-operator" configured
clusterrolebinding "prometheus-operator" configured
service "prometheus-operator" configured
deployment "prometheus-operator" configured
Waiting for Operator to register custom resource definitions..............^C

Then I looked into the deploy and try to run kctl get customresourcedefinitions servicemonitors.monitoring.coreos.com.

ubuntu@test-box:~/prometheus-kubernetes$ kctl get customresourcedefinitions servicemonitors.monitoring.coreos.com
kubectl get customresourcedefinitions servicemonitors.monitoring.coreos.com
Error from server (NotFound): customresourcedefinitions.apiextensions.k8s.io "servicemonitors.monitoring.coreos.com" not found

My kubectl version,deployed on AWS instance.

Client Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.2", GitCommit:"bdaeafa71f6c7c04636251031f93464384d54963", GitTreeState:"clean", BuildDate:"2017-10-24T19:48:57Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.2", GitCommit:"bdaeafa71f6c7c04636251031f93464384d54963", GitTreeState:"clean", BuildDate:"2017-10-24T19:38:10Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}