My GCP GKE cluster is connected to the Rancher (v 2.3.3) but it shows unavailable with the msg: Failed to communicate with API server: Get https://X.x.X.x:443/api/v1/namespaces/kube-system?timeout=30s: waiting for cluster agent to connect

When I try to connect to the GCP K8s Cluster via gcloudshell I cannot retrieve any info with command: kubectl get nodes !!

Any idea why it is happening ... all workloads and services are running and green, only Ingress stuff is with warning info some of them with Unhealthy status from the backend services. But first need to know how can I troubleshoot the problem with connectivity to the k8s cluster with gcloud or rancher !!