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Copilot Studio GCC - Agent cannot access sharepoint site set as knowledge source

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Posted on by CL-27071933-0

Hello,

My agent has been working fine, until Thursday, 7-23-2026. now I am getting the following error message when I test the agent inside Copilot Studio.

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A configuration issue is preventing authentication - check the error message from the server for details. You can modify the configuration in the application registration portal. See https://aka.ms/msal-net-invalid-client for details. Original exception: AADSTS700277: The 1P application xxx-xxx-xxx-xxx-xxx (in the context of 'xxx-xxx-xxx-xxx-xxx') is not allowed to federate cross-cloud from login.microsoftonline.us to microsoftonline.com to access 'xxx-xxx-xxx-xxx-xxx' in the 'xxx-xxx-xxx-xxx-xxx'. Scenario: MSS-to-customer app (including GCC) not allowlisted. Trace ID: xxx-xxx-xxx-xxx-xxx Correlation ID: xxx-xxx-xxx-xxx-xxx Timestamp: 2026-07-27 19:25:52Z

Tenant and App IDs removed

Any help would be greatly appreciated.

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Prasad-MSFT Microsoft Employee on at

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Thanks for sharing the error details. Since you mentioned the agent was working until 23 July and then started failing without any configuration changes, could you confirm a couple of things?

Has anything changed recently in your GCC tenant (e.g., app registrations, SharePoint permissions, or knowledge source configuration)?

Does the issue occur with all SharePoint knowledge sources or only this specific site?

Have you tried creating a new agent or adding a different SharePoint site as a knowledge source to see if the same error occurs?

The AADSTS700277 error suggests a cross-cloud authentication issue (login.microsoftonline.us to microsoftonline.com), which may indicate a service-side or tenant configuration problem rather than an issue with the agent itself.

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CL-27071933-0 4 on at

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Thank you, here is what I have tried so far:

- No changes made to the tenant

- All SharePoint knowledge sources

- I did try to create a new agent, it had the same error message.

- All agents that use a SharePoint site as knowledge sources are receiving this error message

- The error message is only present while testing the agents in Copilot Studio. When tested through the Teams app, the users just see the standard "I'm sorry, I'm not sure how to help with that. Can you try rephrasing?" response.

Both the Copilot Studio and the SharePoint reside within our GCC tenant, so there should not be anything coming from outside of it.

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CS-30032143-0 6 on at

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This started occurring in our tenant as well. Same time. Thursday, 7/23

I have an open support ticket, currently awaiting more feedback. The initial feedback is that enhanced search features such as tenant graph grounding are not available in GCC. If going to Settings > Generative AI > scroll to bottom and untoggle "Tenant graph grounding with semantic search" this does resolve the problem, however this also provides inferior search results than with it toggled on.

Per the documentation, this feature is listed as not available in GCC, however it's been available for months in our tenant. If this is to be the official answer, this will be the 3rd feature we've seen appear for months only to be yanked from us. Not a great end-user experience. So hoping to hear something more positive regarding this issue.

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CL-27071933-0 4 on at

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My issue was resolved with the Advisory PC1440747 fix.

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