Fix Microsoft Office 365 for Mac Authentication Error After Sign-In
Question details
Resolve the Microsoft Office 365 for Mac authentication error that appears after sign-in because of expired authentication tokens or damaged Office credentials stored in macOS Keychain.
- Product
- Microsoft Office 365 for Mac
- Device & OS
- macOS
- Scenario
- A Microsoft 365 subscriber opens Word, Excel, or PowerPoint on a Mac, and the app suddenly asks for sign-in.
- Observed behavior
- Office displays an authentication error even when the correct Microsoft 365 credentials are entered, often caused by an expired Office authentication session or damaged Keychain entries.
Before you start, confirm that your Microsoft 365 subscription is active and that you know the account email and password you use for Office. Close every Office app and prepare to sign in again after clearing stale credentials.
Sign Out of Office and Clear Stale Office Credentials in macOS Keychain
Use this first when Office 365 for Mac requests sign-in and then displays an authentication error even though the password is correct.
The error is often caused by an expired Office authentication token or by damaged Microsoft Office identity entries in the macOS Keychain. Removing only the stale Office credentials lets Office request a fresh token.
Select each Office app in the Dock, right-click its icon, and choose Quit. Alternatively, click the app name in the menu bar, such as Word, and select Quit Word.
Open Word, click Word in the top menu bar, and select Sign Out. Close the app again after signing out.
Press Command+Space to open Spotlight, type Keychain Access, and press Return.
In Keychain Access, select the login keychain and the Passwords category. Search for Microsoft Office, Microsoft Identity, ADAL, or Office entries, then delete only the damaged or outdated Office-related credentials.
Choose Apple menu > Restart. After restarting, open Word and sign in with the same Microsoft 365 account when prompted.
Repair or Recreate the Affected macOS User Profile
Use this when the authentication error appears only in one macOS user profile or persists after clearing Office credentials.
Switch to WPS Office for Mac When Microsoft 365 Sign-In Errors Block Your Work
If Microsoft Office 365 for Mac keeps showing authentication errors, WPS Office for Mac is a free, lightweight alternative that opens Word, Excel, and PowerPoint files with a familiar interface and smooth migration.
- 1. Download WPS Office for Mac: Go to the official WPS Office website and download the free Mac version.
- 2. Open your existing Office files: Launch WPS Office and open DOCX, XLSX, or PPTX files from your Mac.
- 3. Continue editing with familiar tools: Use the ribbon-style interface to edit, save, and share documents without the Office 365 sign-in dependency.
Frequently Asked Questions
Why does Office 365 for Mac show an authentication error after I enter the correct password?
It usually means the Office authentication token or the Microsoft Office credentials stored in macOS Keychain have expired or become damaged. Clearing the stale Office entries and signing in again forces Office to request a new token.
How do I clear Microsoft Office credentials from macOS Keychain?
Open Keychain Access from Spotlight, choose the login keychain and Passwords category, search for Microsoft Office, Microsoft Identity, ADAL, or Office, and delete only the damaged Office-related entries. Then restart the Mac and sign in again.
Will reinstalling Microsoft 365 fix the authentication session expired error?
Not always. Reinstalling can refresh the app, but stale credentials in the macOS Keychain can remain. Sign out of Office, remove the damaged Office credentials, restart, and sign in again before recreating a user profile.
What should I do if Office only fails to sign in on one macOS user account?
Test another macOS user profile. If Office signs in normally there, the original profile likely has damaged credential storage; repair that profile or create a new one with Migration Assistant.
Can WPS Office for Mac open Microsoft Word, Excel, and PowerPoint files if Office 365 cannot sign in?
Yes. WPS Office for Mac can open, edit, and save DOCX, XLSX, and PPTX files and is free to download from the official WPS site.
