This one shows up in a specific, fairly common scenario: someone's display name or email address was changed in your organization's Microsoft 365 admin settings (for example, after a legal name change, a department transfer, or a typo correction), and shortly after, that person starts seeing a 404 error specifically when trying to access the OneDrive tab or files section inside Teams — even though OneDrive works fine on its own, and Teams works fine for chat and meetings.

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Why this happens

Behind the scenes, SharePoint and OneDrive maintain an internal user ID record (sometimes called the UserInfo list) tied to each person's account. When a user's identity details — particularly email or User Principal Name — get changed, this internal record doesn't always update immediately or automatically across every connected service. Teams' OneDrive integration specifically relies on this mapping to know which OneDrive/SharePoint identity corresponds to which Teams user.

If the mapping becomes stale — still pointing to the old identity details — Teams can fail to correctly resolve where to find that user's OneDrive files, resulting in a 404 (essentially "this doesn't exist," even though it does, just under a record Teams can no longer correctly match).

Fix: run Microsoft's Site User ID Mismatch diagnostic

Microsoft provides an official, supported diagnostic tool specifically built for this exact scenario — a deleted/recreated or identity-changed user where SharePoint/OneDrive still holds outdated internal ID information.

  1. This diagnostic needs to be run by an admin, typically through the Microsoft 365 admin center or via the SharePoint Online diagnostics available to your organization's IT team.
  2. If you're the affected user rather than the admin, the most direct path is reporting the issue to your IT department with the specific detail that your name/email was recently changed and you're now seeing a 404 in the Teams OneDrive tab — that detail alone often points IT straight to the right diagnostic rather than generic troubleshooting.
  3. Once the diagnostic completes, changes can take up to 24 hours to fully propagate across SharePoint and OneDrive — so don't expect an instant fix even once the diagnostic has been run.

Note: this diagnostic is not available in certain specialized/sovereign cloud environments (such as GCC High, DoD, or 21Vianet-operated Microsoft 365 in China). If your organization operates in one of these environments and this fix isn't available, a manual support case with Microsoft is typically the next step.

A quicker workaround while waiting

While the proper fix propagates, clearing the Teams cache sometimes restores partial access in the meantime, since it forces Teams to re-fetch identity and permission data rather than relying on a stale local cache:

  1. Fully close Teams
  2. Press Windows key + R, type %appdata%\Microsoft\Teams, press Enter
  3. Delete the contents of the folder
  4. Reopen Teams and sign back in

This isn't guaranteed to fix the underlying identity mismatch, but it's a quick, harmless thing to try while the proper diagnostic and propagation period plays out.