A Slack outage Monday, the first workday of 2021, caused disruptions for remote workers who rely on the platform to message and video chat with colleagues.
Millions of people use Slack, and the service has been especially important during the Covid pandemic.
The outage began around 10 a.m. ET, but service started to resume about three hours later.
Slack shares were down nearly 1% in afternoon trading.
In September 2019, Slack's stock fell 14% after the quarterly earnings report revealed that it took an $8.2 million hit to revenues because of credits to customers after service-level disruptions. Credits help companies cover future bills.
During the outage, Slack's status dashboard said there were problems with Messaging and Connections but did not say what caused the issues or when chat should return to normal.
In an update on the outage at 1 p.m. ET, Slack said: "Some customers may be able to connect, but may also experience degraded performance. We're continuing to work to resolve the issue."
As of late March, Slack said the company's app had 12.5 million simultaneously connected users.