Here’s why Microsoft Teams was down for several hours on the night of July 20th

Arif Bacchus

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No, you were not alone! Microsoft Teams and several other Microsoft 365 apps went down on the night of Wednesday, July 20th, causing frustrations for many people. While the issue has been fixed, Microsoft has since updated customers on what went wrong on their end to cause all these issues (via ZDNet.)

Per a tweet from the Microsoft 365 Status account, it seems as though Microsoft messed up a recent deployment, and it had a broken connection to an internal storage service, which resulted in an impact on services. Microsoft later fixed this issue by directing traffic to a healthy service to mitigate the impact. Teams, Exchange Online, Microsoft Word, Forms, Graph API, Office Online, SharePoint, Project Online, Power Platform, and PowerAutomate, Yammer, and Windows 365 were all impacted because of this.

Initial reports of issues began around 9:47 PM ET on July 20th, and the problem was resolved for most people by 2:15 AM ET on July 21. Some users still report issues with Teams as of the morning of July 21, however. The Microsoft 365 admin center still lists advisories for Microsoft Teams and these other apps.  Microsoft says that service availability across regions is staying above 99%, and will monitor to apply targetted mitigations for residual impacts.