Excel and PowerPoint enter an infinite sign-in loop

The infinite sign-in loop in Excel and PowerPoint on Mac is consistent with a corrupted local identity cache or keychain/credential issue, even though Word is activated and Office Home 2024 is correctly associated with the Microsoft account.

Follow these steps on the Mac (they are safe for data but will sign out Office apps):

1. Quit all Office apps (Word, Excel, PowerPoint, Outlook, OneNote).
2. Clear local identity caches used by Office sign-in:
   • In Finder, open the user folder, then go to:
     • ~/Library/Group Containers/UBF8T346G9.Office
   • Within that path, locate and remove the folders that correspond to identity cache and OneAuth (per the guidance shared via Microsoft Support in similar cases):
     • identitycache
     • oneauth
   • If these folders are not present, skip this step.
3. Reset keychain permissions if Office keeps asking to sign in or shows “Authentication Expired” behavior:
   • This pattern on Mac is documented as being caused by Office being moved or keychain permissions being out of sync.
   • Use the steps in Office for Mac repeatedly requesting keychain access (linked from the activation troubleshooting article) to reset keychain permissions and allow Office apps to access the keychain again. See: Office for Mac repeatedly requesting keychain access.
4. Reopen Word, sign in with the same Microsoft account used to purchase Office Home 2024, and confirm Word still shows Office Home 2024 as activated.
5. Open Excel and PowerPoint and sign in when prompted with the same account. The sign-in loop should be resolved because the corrupted identity cache and keychain issues have been cleared.

If Excel and PowerPoint still loop after these steps, completely remove and reinstall Office for Mac using the documented removal/reinstall procedure, not just a simple drag-to-trash:

1. Close Word, Excel, PowerPoint, Outlook.
2. In Finder → Applications, control‑click Word, Excel, PowerPoint, Outlook and choose Move to Trash.
3. Download the appropriate Office 2024 for Mac installer from Microsoft (for Office Home & Business / perpetual license) as documented, for example:
   • Office 2024 for Mac Installer
4. Run the installer, then start Word and sign in with the Office Home 2024 account to activate.
5. Test Excel and PowerPoint again.

If the problem persists even after clearing identity cache, resetting keychain permissions, and a full reinstall, provide the existing request number and updated details to Microsoft Support so they can review activation logs and licensing status server-side.

References:

• What to try if you can't install or activate Office for Mac
• Microsoft Office activation and the Mac App Store
• Sign in issues when activating Microsoft 365 Apps
• How to fix the issue with MS Office asking you to log in every time you open an Office app - Microsoft Q&A