Office for Mac "Unknown error, the error code is 0x0": how to fix it

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Error 0x0 in Office for Mac is a generic licensing failure, not a sign of damaged files. Microsoft has a known-issue page for it, now marked Resolved, and the fix it gives is to update Office on macOS 12 or later. Office 2019 users should try the same update first.

Applies to:Microsoft 365 / Office for Mac (Word, Excel, PowerPoint, Outlook, OneNote)Office 2019, 2021, 2024 and Microsoft 365 on macOS 12 or later
On this page

What it means

The message reads "UNKNOWN ERROR: An unknown error has occurred. The error code is: 0x0." The code itself tells you nothing. Here it works as a catch-all for a licensing or activation failure in Office on a Mac. It is not a document-corruption error, and your files are not being deleted.

Microsoft documents this in a known-issue page titled Unknown Error 0x0 or License not found error in Microsoft 365 or Office running on macOS. The page is marked Resolved, lists no cause, and gives an update as the fix. It requires macOS 12 or later.

Some people in Microsoft Q&A suggest the trigger was a replaced licensing certificate, which older builds could not pick up. That is an unconfirmed community theory (one forum member quoting Microsoft Copilot), not something Microsoft states. Dates and build numbers also vary between community posts, so treat them as approximate.

Symptoms and causes

You are likely dealing with this problem if:

  • The 0x0 "unknown error" dialog appears when you start an Office app, sign in or activate.
  • Word opens documents read-only and asks you to activate.
  • Some Office apps quit on their own.
  • Sign-in loops back to the start, while Teams or other apps still work with the same account.

The usual causes, most common first:

Outdated Office build
Microsoft's known-issue page lists updating Office as the fix, which points to an old build failing license checks. The page does not name a cause. A community theory blames a replaced licensing certificate, but this is unconfirmed.
Office 2019 for Mac
Microsoft's page lists Office 2019 Excel as affected, with the same update steps. A moderator in Microsoft Q&A said Microsoft had reportedly confirmed 2019 could not be fixed. Treat that as a secondhand claim and try the update anyway.
Older macOS
Microsoft's page requires macOS 12 or later. Macs on an older macOS are outside what the page covers.
Duplicate or stale installs
Copies installed from both the App Store and Microsoft.com can conflict. This comes from a third-party source and is unverified.
Wrong account
Signing in with an account that does not hold the license, or a work or school account with no license assigned. Also from third-party sources and an older, unexplained 2020 report.

How to fix it

Work through these in order. They start with the quickest, safest checks and move to deeper repairs; stop as soon as the problem is gone.

1.Check your macOS and Office versions

Easy

Microsoft's fix needs macOS 12 or later, so confirm that first.

  1. Click the Apple menu and choose About This Mac. Note the macOS version. Microsoft's known-issue page requires macOS 12 or later.
  2. Open Word and choose Word > About Word. Note the Office version and whether it is Office 2019 or Microsoft 365.
  3. On macOS 12 or later, go to the next solution, whatever your Office edition. If your macOS is older than 12, see the last solution.

2.Update Office

Easy

This is the fix given on Microsoft's known-issue page, including for Office 2019 Excel.

  1. Quit all Office apps.
  2. If Office came from Microsoft.com: open Microsoft AutoUpdate (in Applications) and click Update All.
  3. If Office came from the Mac App Store: open the App Store, go to Updates, and update each Office app.
  4. Restart the Office app and sign in again. If it still fails, check Software Update in System Settings, because some people in Q&A also had to update macOS first. Some App Store users then hit an "Apple ID doesn't match" message.

3.Check the account and license

Easy

If the wrong account is signed in, Office has no license to validate.

  1. Sign in with the account that owns the subscription and confirm the subscription is active at account.microsoft.com/services.
  2. For a work or school account, ask your administrator to confirm a license is assigned to you.
  3. Optionally run Microsoft's Support and Recovery Assistant (SaRA), which a Q&A responder suggested.

4.Do a clean reinstall (Microsoft 365)

ModerateChanges settings

Removes stale or duplicate copies and installs the current build. This step comes from a Q&A thread, not from Microsoft's known-issue page.

Before you start: Save your documents outside the Office apps first. One user in Q&A uninstalled Office on an older macOS and could not reinstall it, so check the installer's system requirements before you remove anything. This applies to a Microsoft 365 subscription, not Office 2019.

  1. Drag all Microsoft Office apps from Applications to the Trash, check for duplicate copies, then empty the Trash.
  2. Sign in at account.microsoft.com/services and download the installer from Subscriptions.
  3. Install, open an app and sign in with the subscription account.

5.If the update does not work (Office 2019 or macOS below 12)

Moderate

If Update All does not clear the error, or your macOS is older than 12, the realistic choice is a workaround.

  1. Use Microsoft 365 for the web to open and edit your files in a browser.
  2. Or move to a supported setup: buy a newer Office or Microsoft 365, or upgrade macOS if your Mac allows it.
  3. A moderator in Q&A named builds 16.88 (for macOS Monterey) and 16.101 (for Ventura) as the last ones for those systems. This is one moderator's claim and not checked against Microsoft documentation, so confirm on Microsoft's own pages before relying on it.
  4. Other workarounds people mention are a Windows virtual machine or LibreOffice.

Check that it worked

  • Open Word, Excel or Outlook: the 0x0 dialog no longer appears.
  • Documents open for editing, not read-only, and sign-in completes without looping.

If it still fails

  • Note your exact macOS and Office versions, then post them in Microsoft Q&A or contact Microsoft support.
  • Signing out and back in, deleting Keychain entries and running the license removal tool are sometimes suggested elsewhere, but users in the Microsoft thread reported they did not help with this issue.
  • If you are on Office 2019 or a macOS older than 12 and Update All did not help, use the web version or upgrade.

Questions

Did I lose my documents?

No. Reports say files are not deleted. The error only affects licensing.

Is 0x0 on Windows the same problem?

No. This article covers Office for Mac. Windows codes like 0x426-0x0 are a different problem and are not covered here.

Sources

  1. Unknown Error 0x0 or License not found error in Microsoft 365 or Office running on macOSOfficial · Microsoft Support
  2. 0x0 Error After Mac Update July 14th, 2026 · Microsoft Q&A (community and moderator answers)
  3. Error Code 0x0 during login on Mac · Microsoft Q&A (community)
  4. Microsoft 365 activation problem · Microsoft Q&A (community)
  5. Office Mac "Unknown Error 0x0" and "License Not Found" fix · Office Watch
  6. Office Error Code 0x0 on Mac · Wondershare Recoverit

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