@Eric VILLARS, Thanks for posting in Q&A. The error codes you are encountering during the update of Office 365 with Intune indicate that Office applications are open and need to be closed before the update can proceed. The error code 0xFFFFFFFF is an unknown error and may require further investigation. To troubleshoot the issue, you can try closing all Office applications and then attempting the update again. If the issue persists, you can try capturing verbose installation logs to get more detailed information on the error. To do this, follow the steps outlined in the "Capture Office installation verbose logs during the installation" section of the "Add Microsoft 365 Apps to Windows 10/11 devices with Microsoft Intune" document.
https://learn.microsoft.com/en-us/mem/intune/apps/apps-add-office365#troubleshooting
Hope the above information can help.
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