Slack started experiencing performance issues early Monday morning, impacting remote workers that rely on the service.

Slack is locked in a battle with Microsoft Teams for the corporate messaging market. While the service is widely popular, it can’t afford errors or missteps that Microsoft could capitalize on.

Unfortunately, Monday morning the service was experiencing significant performance issues impacting all three of its target platforms.

Some users may be experiencing slowness with Slack in the desktop, browser and mobile at this time. The issue is impacting sending messages and troubles with API calls.

As of mid-afternoon, the issues were declining, although many customers were still not seeing any improvement. The company had also not indicated what underlying issue caused the problem.