Excel Trying to Access External Tenant

Question

In trying to open an Excel file from a contractor, I got an error that there was trouble signing me in. It mentions that I don't exist on the contractor's tenant (which is correct), but now I can't even open a new sheet in Excel without receiving this error. All other MS products are fine. How can I use Excel for other files?

Answer 1

Hi @Tristanne Staudt,

Welcome to Microsoft Q&A forum.   

Thank you for reaching out. I understand that you’re seeing a sign‑in error in Excel after opening a file from an external contractor, and now even new blank workbooks are triggering the same message.

When you open a file located in another organization’s OneDrive or SharePoint, Entra ID (Azure AD) attempts to authenticate you against that organization’s tenant. If your account isn’t added there as a guest, the authentication fails. Sometimes Excel also retains old identity tokens and keeps sending the request to the wrong tenant, which leads to the same sign‑in error even when you’re working with completely local files.

Here are a few suggestion steps you can try to fix the issue:

1/ Sign out of the incorrect account in Excel

• Open Excel
• Go to File > Account and sign out of all accounts shown under User Information
• Select your name/photo in the top‑right corner and remove any extra work or school accounts
• Sign back in using only your organization’s account

2/ Remove any external organization connection from Windows

• Open Windows Settings > Accounts > Access work or school
• If you see the contractor’s organization listed there, select it and choose Disconnect

3/ Clear Office identity and credential cache

a. Close all Office apps

Make sure Word, Excel, Outlook, Teams, and OneDrive sync client are completely closed.

b. Remove Office identity cache from Registry

1. Press Win + R, type regedit, and press Enter
2. Delete this key (it will be recreated automatically):

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity

c. Delete OneAuth / IdentityCache folders

Delete all folders inside:

%localappdata%\Microsoft\OneAuth 
%localappdata%\Microsoft\IdentityCache

d. Clear Office credentials in Credential Manager

• Go to Control Panel > Credential Manager > Windows Credentials
• Remove any credentials related to:
  • MicrosoftOffice
  • Office
  • ADAL
  • OneDrive
  • Your organization’s cloud apps

Restart Windows afterward.

4/ Re‑open Excel and sign in with your correct work account

• Open Excel
• Go to File > Account and sign in with your company account
• You should now be able to open new and local files normally

If Excel still shows sign‑in issues, you can run Microsoft’s activation/sign‑in reset tool (SaRA or the Get Help activation troubleshooter) to clear old authentication tokens: Reset activation state for Microsoft 365 Apps for enterprise.

 

If you still need to open the contractor’s file, ask the contractor to:

• Add you as a guest to their tenant, or
• Share the file using a link you can access, or
• Send a local copy of the file.

I hope this information helps. Please try the steps and let me know whether they resolve the issue. If the problem persists, we can work together to find a solution.  

As other users will also search for information in this community, your vote can significantly help those with similar inquiries quickly locate the most relevant resources. 

Thank you for your kindness and for contributing to the forum.   

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