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So much for "team" work. Microsoft Teams experienced an outage Monday with its business-oriented communications and collaborative platform and rival to Slack.

Microsoft said that the issue was related to an expiring "authentication certificate," and that it was working on a replacement that would "remediate impact."

Some had been able to get into Teams through the Teams app on the phone, but not through the desktop app.

Service on the Teams desktop was restored for at least some folks around 11:30 a.m, east coast time, as Microsoft rolled out its fix.

"We're sorry—we've run into an issue," is the message users saw when they tried to log in from the desktop app earlier in the day.

The outage was felt globally, with users on the Downdetector.com site reporting Teams having been down in Florida, Texas, Oklahoma, Germany and Italy.

Microsoft's explanation for the Teams invited scorn on social media.

"Microsoft Teams goes down after Microsoft forgot to renew a certificate. That's embarrassing!," tweeted Kevin Shoaf.

Business people felt the pain of the Teams' disruptions.

Teams user Andrew Choi tweeted, "Microsoft Teams, what now? We have a meeting and can't proceed of it. Ugh."

Another user, E-C, tweeted, "Microsoft Teams is down and I feel lost."