Microsoft Teams service down as it forgets to renew a certificate

Microsoft Teams has fallen off on Monday for nearly three hours after it 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.

Microsoft confirmed the Teams service was down just after 9AM and then later revealed the source of the issue. Microsoft notified that, “We’ve determined that an authentication certificate has expired causing users to have issues using the service.” Microsoft then started rolling the fix out at 11:20AM, and by 12PM the service was restored for most affected users. Microsoft confirmed the fix was successfully deployed at 4:27PM.

Microsoft started its own TV commercials for Teams recently and after that this was an embarrassing situation for Microsoft’s flagship “Office hub” software. It’s also 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.