We've confirmed that all systems are back to normal with no customer impact as of 05/19, 06:02 UTC. Our logs show the incident started on 05/18, 20:49 UTC and that during the ~9 hours 13 minutes that it took to resolve the issue some customers who have configured webhooks to send notifications may not have fired or taken action during the impacted window.
Root Cause: The Failure was due to a downstream Azure Automation service which experienced issues due to configuration changes.
Incident Timeline: 9 Hours & 13 minutes - 05/18, 20:49 UTC through 05/19, 06:02 UTC
We understand that customers rely on Azure Notification Service as a critical service and apologize for any impact this incident caused.
Initial Update: Sunday, 19 May 2019 05:47 UTC
We are aware of issues with Alert Notification with respect to configured webhooks and are actively investigating. Some customers who has configured webhook with the action items may not have receive the alerts.
Work Around: None
Next Update: Before 05/19 08:00 UTC
We are working hard to resolve this issue and apologize for any inconvenience. -Mohini Nikam