How to Fix OneDrive 404 Error When Opening Shared Files - Outlook 404 Not Found on Shared Mailbox: Fixes & Checks-How to Fix Outlook Crashing on Windows 10
Before changing system settings, save your work and note the exact error text so you can compare results after each step.
Extra verification checklist
- Restart the affected app after changing permissions or configuration files.
- Test the same workflow in a clean browser profile or a temporary user account.
- Compare the result on another network if the error may be connection related.