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It seems from your query that you're having trouble enabling the managed Prometheus.
When you create a new AKS cluster in the Azure portal, you have to enable Prometheus, Container insights, and Grafana from the Monitoring tab. Make sure that you check the Enable Container Logs, Enable Prometheus metrics, and Enable Grafana checkboxes. As shown in below image.
Please refer to this link for detailed information: https://video2.skills-academy.com/en-us/azure/azure-monitor/containers/kubernetes-monitoring-enable?tabs=cli#enable-full-monitoring-with-azure-portal
Ensure that you have Contributor RBAC permissions to enable managed Prometheus and required Monitoring Reader or Monitoring Contributor to view data after monitoring is enabled.
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