“ERR_BLOCKED_BY_RESPONSE.NotSameOrigin / CORS Errors in Excel Online”

Question

Hello,

There seems to be a problem with pivot table in web excel. We're using Business Standard version of subscription.

What errors we're getting in devconsole:

1. Failed to load resource: net::ERR_BLOCKED_BY_RESPONSE.NotSameOriginAfterDefaultedToSameOriginByCoep
2. Failed to load resource: net::ERR_BLOCKED_BY_CLIENT
3. 1.0/?cors=true&content-type=application/x-json-str...%3D4%26LU%3D1761123710526&w=0&NoResponseBody=true

What we have tested:

1. Different browsers → same issue everywhere (Chrome, Edge, Firefox).
2. Different computers, including a clean PC with no security software installed → same result.
3. Different network connections, including mobile hotspot, to rule out Router/Antyvirus or any corporate network filtering → same issue.
4. The problem did not exist previously. For one user, switching to a different browser temporarily worked yesterday, but today no browser works at all for anyone.

Request: Please confirm whether there have been any recent changes to:

• CORS / CSP rules cause there seems to be a problem.

Answer 1

The errors you are encountering, such as ERR_BLOCKED_BY_RESPONSE.NotSameOrigin and ERR_BLOCKED_BY_CLIENT, are related to Cross-Origin Resource Sharing (CORS) issues. CORS is a security feature implemented by browsers to prevent malicious sites from accessing resources from another domain without permission. If the CORS headers are not correctly configured on the server, the browser will block the request, resulting in these errors.

Since you mentioned that the issue persists across different browsers, computers, and network connections, it suggests that the problem may not be on the client side but rather related to the server configuration or recent changes in CORS policies.

To troubleshoot this issue further, you can:

1. Check the CORS configuration on the server that is hosting the Excel Online resources to ensure that it allows requests from your domain.
2. Review any recent changes made to the server or application that might have affected CORS settings.
3. Use browser developer tools to inspect the network requests and responses, particularly looking for the Access-Control-Allow-Origin header in the response to see if it is set correctly.

If this problem did not exist previously, it is possible that a recent update or change in the server's configuration or the application itself has introduced this issue.

For more detailed guidance on troubleshooting CORS issues, you may refer to the relevant documentation on CORS and Microsoft Entra ID.

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References:

• Troubleshoot CORS issues with Microsoft Entra ID
• Resolve cross-origin resource sharing issues in Microsoft Entra application proxy

Answer 2

Hi @Mateusz Zajączek,

Welcome to the Microsoft Q&A forum.

Thank you for sharing the detailed information about the issue you are experiencing with pivot tables in Excel for Web. I understand how important this functionality is for your work, and I appreciate the steps you have already taken to troubleshoot the problem.

Based on the error messages and the extensive testing you have performed across different browsers, devices, and networks, this appears to be a complex server-side issue that may require deeper investigation by Microsoft engineers. It could involve backend configurations such as CORS or CSP rules, which are not accessible from the client side.

In the meantime, here are a few workarounds that you could consider:

• Open in Excel desktop: Use File > Open in desktop app for critical PivotTable tasks until the web issue is resolved.
• Try alternate entry points: Open the workbook directly from its OneDrive or SharePoint URL (not via Teams) and sign out/sign in for a fresh session.
• Use InPrivate/Incognito mode and temporarily disable browser extensions (ad blockers, privacy tools) to rule out header injection.

To ensure this is resolved efficiently, I recommend creating a support ticket with Microsoft Support. This will allow the support team to:

• Collect diagnostic logs and environment details.
• Escalate the case to the appropriate engineering team.
• Provide updates and resolution through an official channel.

You can create a support ticket by sign in to the Microsoft 365 Admin Center following steps from this link: Get support - Microsoft 365 admin | Microsoft Learn to raise a support ticket from admin center or calling the phone support to contact Microsoft Support: Customer service phone numbers - Microsoft Support.

If you are not an admin, you can contact your admin to contact Microsoft support. You can look for the way to find your admin through this link: How do I find my Microsoft 365 admin? - Microsoft Support.

Please accept my apologies for redirecting you to the related team support, as the moderators in this community have limited resources and permission to verify the backend information and to get the quick and better assistance, we requested for this.

I hope this information is helpful. If you have any concerns or questions in the future, please don’t hesitate to reach out. Not only will I be happy to assist you, but all moderators in the Q&A forum will also do their best to provide support and guidance.  

Thank you so much for your patience and understanding.

Wishing you a wonderful day ahead and sending warm regards your way.

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