HPA always showing unknown CPU

Whenever I create an HPA, it always shows the TARGET as /3% or similar.

I have metrics-server running in kube-system (created by helm install metrics-server), and when I do a kubectl top nodes I get data back (with no unknowns) as well as when I do a kubectl get --raw "/apis/metrics.k8s.io/"

How can I debug this issue?

Cluster information:

Kubernetes version: 1.13
Cloud being used: bare metal
Installation method: kubeadm
Host OS: centos7
CNI and version: flannel 0.9
CRI and version: docker 18.9

Did you try zahid0’s answer in this github issue?