We've confirmed that all systems are back to normal with no customer impact as of 06/15, 16:00 UTC. Our logs show the incident started on 06/14, 17:00 UTC and that during the 23 hours that it took to resolve the issue some small subset of customers experienced intermittent issues when querying Activity Logs in the Azure Portal.
Root Cause: The failure was due to one of the dependent service failure .
Incident Timeline: 23 Hours & 0 minutes - 06/14, 17:00 UTC through 06/15, 16:00 UTC
We understand that customers rely on Azure Monitor as a critical service and apologize for any impact this incident caused.