Microsoft is investigating an ongoing outage blocking customers worldwide from accessing and using web apps like Excel Online and online services.

The list of affected services includes Microsoft 365 suite, Exchange Online, SharePoint Online, Yammer Enterprise, Planner, Microsoft Teams, Microsoft 365 for the web, and Project for the web.

According to reports, customers are experiencing problems when trying to sign into their accounts and will see that no web apps are available once in.

“We’re investigating access issues with Microsoft 365 Online apps and the Teams admin center. Further information can be found under OO544150 within the Microsoft 365 admin center,” the company tweeted earlier today.

“Users may be intermittently unable to view or access web apps in Microsoft 365. We’re reviewing service monitoring telemetry to isolate the root cause and develop a remediation plan,” the admin center incident report says.

In some cases, a banner displayed at the top of the screen asks “new” users to reach out to their IT department to help with the issue.

“New to Microsoft 365? This is your Microsoft 365 home page where you can see and access all of your apps. If it’s empty, it could be that your user license was very recently assigned to you,” the notification reads.

“Wait 10 minutes and refresh this page. If you still don’t see any apps, contact your IT department. They can help you get up and running.”

We're investigating access issues with Microsoft 365 Online apps and the Teams admin center. Further information can be found under OO544150 within the Microsoft 365 admin center.

— Microsoft 365 Status (@MSFT365Status) April 20, 2023

According to the latest updates provided by Microsoft in the admin center, the out was caused by caching infrastructure performing below acceptable performance thresholds and leading to timeout exceptions.

“Analysis of diagnostic data has identified an unusually high number of timeout exceptions within our caching and Azure Active Directory (AAD) infrastructure. We’re working to isolate the cause of these exceptions whilst identifying steps to remediate impact,” Microsoft said.

Until this Microsoft 365 outage is addressed, users can access applications through direct URLs. Microsoft provides the following examples: