Microsoft Teams went down today for nearly three hours after Microsoft forgot to renew a critical security certificate. Users of Microsoft’s Slack competitor were met with error messages attempting to sign into the service on Monday morning, with the app noting it had failed to establish an HTTPS connection to Microsoft’s servers.
We've determined that an authentication certificate has expired causing, users to have issues using the service. We're developing a fix to apply a new certificate to the service which will remediate impact. Further updates can be found under TM202916 in the admin center.
— Microsoft 365 Status (@MSFT365Status) February 3, 2020
It’s odd that Microsoft would forget to renew a critical authentication certificate, and it was rude timing, as so many were attempting to log in and start their week.
Microsoft confirmed the Teams service was down just after 9AM ET today, and then later revealed the source of the issue. “We’ve determined that an authentication certificate has expired causing users to have issues using the service,” explains Microsoft’s outage notification. Microsoft then started rolling the fix out at 11:20AM ET, and by 12PM ET the service was restored for most affected users.
It’s surprising to see Microsoft forget to renew a key certificate for Teams, especially when the company develops software like System Center Operations Manager to monitor for things like certificate expiration.
