In an embarrassing snafu, Microsoft Teams went down for nearly 7 hours on Monday. The cause? An expired authentication certificate.

What happened? When users attempted to sign in to the service, they received error messages that said the app had failed to establish an HTTPS connection to Microsoft’s servers, the Verge said. Digi Statement had first reported the issue.

It took the company 7 hours to fix the issue: Users on social media had begun reporting issues with the online collaboration platform at 9 am ET (7:30 pm IST) on February 3, and Microsoft acknowledged the issue at 9:19 am ET (7:49 pm IST). It took them about an hour to figure out the issue and another hour to deploy the updated certificate. At 4:27 pm ET (2:57 am IST), the company issued an update that the problem had been resolved. No other Microsoft service was affected.

Irony: Microsoft develops System Center Operations Manager to monitor things like certificate expiration, the Verge noted.