AuthenticationFailed Errors for /{chat_id}/messages Between July 4 and July 12

Question

Hello,

Between July 4 and July 12, calls to the following endpoint failed with an AuthenticationFailed error:

/{chat_id}/messages

The issue occurred across five different tenants at the same time, for the same endpoint, and with the same error.

Based on Microsoft Q&A discussions, it appears that multiple organizations experienced the same behavior during this period. Other endpoints continued to work as expected, there were no permission or configuration changes on our side, and the failures were limited to this specific endpoint and timeframe.
It was resolved on it's own.

Given that several organizations experienced the same issue simultaneously, could you please confirm whether this was unexpected Microsoft behavior that has since been resolved?

Our clients need to explain to their regulators why we were unable to retrieve their data during this period, so an official confirmation would be highly appreciated.

Thank you.

Answer 1

Hi @Eran Otmi

Based on your description, I understand that between July 4 and July 12, 2026, your application experienced consistent AuthenticationFailed errors when making calls to the /{chat_id}/messages Microsoft Graph API endpoint. This issue simultaneously impacted five different tenants, occurred without any internal permission or configuration modifications on your side, and was isolated strictly to this specific endpoint and timeframe. Furthermore, your research on Microsoft Q&A indicates this was a widespread issue affecting multiple organizations globally, and the behavior eventually resolved itself. You are now seeking confirmation of this unexpected service regression to help your clients explain the data retrieval gap to their regulators.

At this point, I would avoid stating that this is officially confirmed as a Microsoft outage unless Microsoft support provides that confirmation through a support case, Service Health communication, or a product group update.As a community forum, it is important to first clarify that moderators and participants here are not official Microsoft representatives and cannot provide an official service incident confirmation for regulatory purposes.

Please open a Microsoft support case from one of the affected tenants and provide request IDs, timestamps, tenant IDs, application IDs, and sample failed responses so Microsoft support can correlate the failures with backend telemetry and provide an official statement if applicable.

Thank you for your patience.

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