Hello,
Welcome to the Microsoft Community Forum. Please accept our warmest regards and sincerest hope that all is well despite the situation you find yourself in.
That sounds incredibly frustrating, especially since it's only affecting one document. Based on similar cases, here are a few possible reasons and solutions:
Possible Causes & Fixes:
- Session Timeout Settings – Some education accounts have stricter session expiration settings. If your institution has enabled IP address enforcement, it could be causing shorter session lifetimes.
- Document-Specific Issue – If other documents work fine, this one might have a corruption issue. Try opening it in Office Online or downloading it to your device.
- Check OneDrive or SharePoint Permissions – If the document is stored in OneDrive for Business or SharePoint, check whether your access permissions have changed.
- Try a Different Network – Some network restrictions can interfere with authentication. If possible, try accessing the document from a different Wi-Fi or mobile network.
- Clear Cache & Cookies – Sometimes, browser cache can cause authentication issues. Clear your cache and cookies, then restart your browser.
- Use PowerShell to Extend Session Lifetime – If your institution manages SharePoint settings, an administrator can extend the session lifetime using PowerShell.
If none of these work, I recommend reaching out to your IT administrator or Microsoft Support for further troubleshooting.
Hope this helps.
Best Regards,
Fordy B.
Microsoft Community Moderator