Microsoft says a recent update has affected the processing of authentication requests, making cloud-based services inaccessible.
Microsoft said people who were logged into an existing 365 session were still able to keep using the service.
“Starting at approximately 21:25 UTC, a subset of customers in the Azure Public and Azure Government cloud may encounter errors performing authentication operations for a number of Microsoft/Azure services, including access to the Azure Portals,” the company said in a status post.
Microsoft customers started reporting their inability to access Office 365 on Downdetector.com at 5:21 pm—within an hour, more than 18,000 posts documenting those problems had flooded the website that tracks cloud outages.
“Existing customer sessions are not impacted and any user who is logged in to an existing session would be able to continue their sessions,” Microsoft said.
By 00:40 UTC, Microsoft said it was seeing improvement across multiple services.
“We’re continuing to see significant improvement for affected services and most users should be experiencing relief,” Microsoft added at 1:20 UTC.
At 3 am UTC, Microsoft reported the services were mostly restored, but a small subset of customers in North America and the Asia Pacific were still unable to access services.
At 4:00 UTC, the company said the issue was resolved.
“We’ve confirmed that the residual issue has been addressed and the incident has been resolved. Any users still experiencing impact should be mitigated shortly,” it said.