Yesterday, Microsoft Teams—a combination instant messaging, chat, and collaboration package competing with Slack and the new version of Google Hangouts—was inaccessible for several hours, from approximately 8:30am to 11:30am ET.

By 10:30am, Microsoft acknowledged on Twitter that the outage was the result of an expired SSL certificate. Approximately an hour later, they had secured a replacement certificate and began deploying it in production, with service widely restored by Monday afternoon.

This isn’t Microsoft’s first major public embarrassment due to a service renewal failure. The company was responsible for one of the most famous “oops, we accidentally the whole domain” incidents in 1999, when it allowed the domain registry for passport.com to expire. The domain was responsible for authentication for a variety of Microsoft services, including Hotmail.com and Microsoft Messenger.