I can't seems to install rancher-monitoring. My rancher manager has this to say :

[ERROR] error syncing 'cattle-monitoring-system': handler namespace-auth: Internal error occurred: failed calling webhook "rancher.cattle.io.namespaces": failed to call webhook: Post "<https://rancher-webhook.cattle-system.svc:443/v1/webhook/validation/namespaces?timeout=10s>": context deadline exceeded, requeuing

And afterwards, the installation fails because of

namespaces "cattle-dashboards" not found