Several Microsoft business and consumer cloud services, including Office 365 storage and email services, were inaccessible on Tuesday due to problems authenticating users.
The widespread outage has prevented customers from accessing OneDrive storage, Skype collaboration, Outlook email, and consumer products such as Xbox Live.
The Office 365 status page acknowledged a problem that began at 12:15 US Eastern time, but didn't offer an expected resolution time. Microsoft has made no further announcements related to the cloud failure.
Twitter users reported the problems appear to involve authenticating their accounts when trying to sign into those services through their identity management portals.
That's reminiscent of an hour-long outage two weeks ago, where users with Microsoft Managed Service Accounts (MSAs), which essentially implement Active Directory authentication for individual computers, couldn't log into their accounts.