Rancher got: x509: certificate signed by unknown authority

Rancher 2.x
1

I download the kubeconfig file and when I run kubectl get nodes,
I got Unable to connect to the server: x509: certificate signed by unknown authority.

certificate is signed by let’s encrypt
This is my architecture:
https://www.cnrancher.com/docs/img/rancher/ha/rancher2ha.svg

2

Please supply the exact commands used to setup Rancher HA, that will show what might have gone wrong and will show the versions used.