Your clusters needs a default storage class for the Kubecost and Prometheus persistent volumes to be successfully attached.
To check if a storage class exists, you can run
kubectl get storageclass
You should see a storageclass name with (default) next to it as in this example.
NAME PROVISIONER AGE standard (default) kubernetes.io/gce-pd 10d
If you see a name but no (default) next to it, run
kubectl patch storageclass <name> -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
If you don’t see a name, you need to add a storage class. For help doing this, see the following guides: