Can't Log in to 365

Question

I am unable to log in to my Microsoft 365 account. The error message I'm getting is 0x0. Can you help me?

Thanks,

Don

Answer 1

Dear Don,

Good day, and thank you for reaching out to the Q&A Forum. The 0x0 error on macOS is a widely reported Microsoft 365 / Office for Mac activation issue that started on July 13, 2026, when Microsoft replaced the licensing certificate for Office apps on macOS. Microsoft has since marked the issue as RESOLVED, with the fix delivered through application updates. As a forum moderator, I genuinely wish I could directly access your account or delve into the backend systems to diagnose and fix this for you. However, my role here is limited to providing general guidance and solutions that can be applied by users. Based on Microsoft's official guidance, the resolution depends on your macOS version and how you originally installed Office:

1.Make sure you are running macOS 12 (Monterey) or later. This is the minimum required version for the fix to apply.

2.If you installed Microsoft 365 or Office from microsoft.com:

• Close all Office applications
• Open Microsoft AutoUpdate (MAU) from Finder > Applications > Microsoft AutoUpdate
• Click Update All (or update idividual apps) and wait for the updates to complete
• Launch an Office app to test.

If your Mac cannot be updated to macOS 12 or later, unfortunately Office apps on that device will enter reduced functionality mode, and the licensing update cannot be applied. Your options in that case would be:

• Use Microsoft 365 on the web
• Use Office on a different supported device
• Upgrade your Mac to a supported version

For references: 

Certificate update for Microsoft 365 apps on managed macOS and iOS devices - Microsoft 365 Apps

Update Microsoft 365 or Office on your macOS or iOS device | Microsoft Support

Unknown Error 0x0 or License not found error in Microsoft 365 or Office running on macOS

For additional community-tested solutions tailored to specific macOS versions, please also check Emily's answer on this thread, which summarizes the most common working paths depending on your OS version and Office installation method: 0x0 Error After Mac Update July 14th, 2026 - Microsoft Q&A

I hope this information helps clarify the situation and provides you with workable solutions. Should you have any further questions or need additional assistance, please don't hesitate to reach out. I'm always happy to help. Have a wonderful day! 

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