Getting error: no unmonitored services found, no vanished services found [special_kubernetes] Agent exited with code 1: (404)

Troubleshooting
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Also, the IP address of the API server differs from within the cluster to outside the cluster.
As you have deployed Checkmk within Kubernetes, you also need to use the ClusterIP of the kubernetes service, e.g.
mh@klapp-0141:~$ kubectl get svc kubernetes
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.100.0.1 443/TCP 105d