Microsoft Teams went down for several hours Monday morning after infrastructure problems forced some traffic to be diverted, giving users who don’t have President’s Day off a little extra downtime.

Microsoft’s workplace collaboration tool was inaccessible for at least three hours as of publishing time, which the company attributed to unspecified infrastructure issues. “We’ve rerouted traffic to healthy infrastructure which has improved Teams connectivity issues,” the company said as of 930am PT Monday, although it has yet to sound an all-clear.

Teams is Microsoft’s attempt at denting the momentum of Slack, which captivated Silicon Valley over the last few years with its chat and collaboration tools. Slack is used by 10 million daily active users and 85,000 paying customers, while Teams has seen a lot of adoption over the past year thanks to its integration with Office 365.

Slack has also struggled with uptime over the years, with minor outages cascading into larger issues as users all try to reconnect to the service at the same time. It’s not clear what caused Monday’s issues with Microsoft Teams, although a Teams user posted a screenshot from the service’s internal health dashboard suggesting that a configuration change deployed last week was not the root cause.

We’ll update this post if and when the service returns and Microsoft provides more details on what happened.

Update: 1137am PT: Microsoft appears to have resolved the Teams issues, but let us know if you’re still having trouble.