Microsoft Teams is currently down worldwide 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 Monday morning.

Microsoft Teams is currently down worldwide 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 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 ET today, and then 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. “We’re developing a fix to apply a new certificate to the service which will remediate impact.”


This is an embarrassing mistake for Microsoft to make for its flagship “Office hub” software, especially as the company started its own TV commercials for Teams recently. 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.

At the time of writing Microsoft Teams has been down for nearly two hours, and the company is currently deploying a fix to its servers. We’ll update this article with any relevant changes.

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