We've confirmed that all systems are back to normal with no customer impact as of 01/25, 04:40 UTC. Our logs show the incident started on 01/22, 00:00 UTC and that during the 3 days, 4 hours and 40 minutes that it took to resolve the issue some of customers using Azure Monitor service may have experienced errors when registering subscriptions with the Microsoft Insights Resource Provider, with the state stuck on "Registering". Retries may have been successful.
Root Cause: The failure was due to an issue in one of our dependent services.
Incident Timeline: 3 Days, 4 Hours & 40 minutes - 01/22, 00:00 UTC through 01/25, 04:40 UTC
We understand that customers rely on Azure Monitor as a critical service and apologize for any impact this incident caused.