We've confirmed that all systems are back to normal with no customer impact as of 07/09, 06:30 AM UTC. Our logs show that the incident started on 07/09, 12:00 AM UTC and that during the 6 hours 30 minutes that it took to resolve the issue some customers would have experienced error while accessing Alerts Summary page under Azure Monitor in Azure Portal.
Root Cause: The failure was due to issues in one of our back-end services which went in to unhealthy state
Incident Timeline: 6 Hours & 30 minutes - 07/09, 12:00 AM UTC through 07/09, 06:30 AM UTC
We understand that customers rely on Azure Monitor as a critical service and apologize for any impact this incident caused.