Excel Repeated Login Prompts – Known Microsoft Bug in Versions 2510 and Later

Summary

Microsoft has released an update (Excel version 2510 and later) that introduced a bug affecting authentication tokens for all Excel files that connect to third-party services. This includes EBM cubes and other files that require a Microsoft 365 login.

When using affected versions, users may:

• Be prompted to sign in repeatedly after refreshing, switching tabs, or adding fields to a PivotTable.

• Experience slow performance or lag when interacting with external data connections.

This issue is not specific to EBM — it’s a Microsoft Excel issue currently affecting many organizations.

Recommended Fix – Update or Roll Back

Best path today: update to Version 2510 - Build 16.0.19328.20144 which contains Microsoft’s fix. If you cannot update right away, roll back to Version 2509 and pause updates until you can move to the fixed build.

We’re not confident in any Excel version above 2509 unless it is the fixed build listed above, though we’ve seen isolated cases where reinstalling Microsoft Office temporarily resolves the issue while remaining on the same version.

If you cannot update to the fixed build, our most reliable recommendation remains to roll back to Version 2509 (Build 19231.20156) and pause updates until you can install the confirmed fix.

Option 1 – Roll Back to Version 2509 (Most Reliable)

Rolling back restores Excel to the last stable release prior to the issue.

If your IT department manages Office updates (most common):

Ask IT to run this command on your computer or via Microsoft Endpoint Manager:

cd %programfiles%\Common Files\Microsoft Shared\ClickToRun
officec2rclient.exe /update user updatetoversion=16.0.19231.20156

This will downgrade Microsoft 365 Apps (Excel, Word, etc.) to Version 2509.
Afterward, open Excel → File → Account → About Excel to confirm your version.

If you manage your own Office updates:

1. Close all Office apps.

2. Open Command Prompt as Administrator.

3. Run the same command shown above.

4. Restart your PC and confirm Excel shows Version 2509.

5. Pause Office updates temporarily to prevent reinstallation of Version 2510+ if you cannot install the fixed build yet.

Option 2 – Reinstall Microsoft Office (Temporary Workaround)

Some users have reported temporary success by reinstalling Office without rolling back.
This may reset corrupted authentication components introduced during the update process.

To reinstall Microsoft Office:

1. Open Control Panel → Programs → Programs and Features.

2. Select Microsoft 365 Apps (Office) and click Uninstall.

3. Once complete, reinstall Office using your organization’s portal (e.g., portal.office.com) or Microsoft 365 installer.

4. Reboot your device, then open Excel → File → Account → About Excel to confirm your version.

⚠️ Note: This approach may temporarily fix the issue but is not a guaranteed or permanent solution. We recommend rolling back to Version 2509 if problems persist after reinstalling.

EBM has submitted tickets with Microsoft and is in communication with their support team regarding this issue.

What You’ll See

Typical symptoms include:

• Continuous login prompts even after successful sign-in.

• Reauthentication loops after a refresh, field update, or tab switch.

• Excel becoming unresponsive or slow to refresh.

These behaviors occur because Microsoft’s new authentication logic in version 2510 mishandles 365 tokens used for external data sources like Azure Analysis Services, Power BI connections, and third-party add-ins.

Additional Steps (If Rolling Back Is Not Possible)

If your organization cannot roll back right away:

1. Sign out of all accounts in Excel and Windows and sign back in with your primary Microsoft 365 account only.

2. Clear cached credentials in Windows Credential Manager.

3. Repair Office via Control Panel → Programs → Microsoft Office → Change → Repair.

4. Reinstall Microsoft Office as outlined above (this may help temporarily if rolling back is not allowed).

5. Contact your IT administrator to verify token lifetime and SSO policies.

Microsoft Status

Microsoft is aware of the problem and investigating it under internal bug reports related to authentication token handling in Excel 2510+. We’ll update this article once an official patch or release is confirmed.

Related Articles

For background on how this issue has manifested in previous versions or environments, refer to our original guide: 
🔗 Repeated Login Prompts in Excel When Accessing EBM Cubes

Need Help?

If you’ve verified your Excel version and still experience repeated login prompts, please reach out to EBM Support for further assistance: Submit a Request →

Include in your ticket:

• Your Excel version number (File → Account → About Excel)

• Whether you’ve rolled back, reinstalled, or repaired Excel

• Any relevant screenshots or file examples

This issue affects any Excel file with an external connection that uses Microsoft 365 authentication — not just EBM cubes. Once Microsoft releases a stable fix, EBM will update this article and notify affected clients.