Some users may be unable to access Microsoft 365 Copilot Chat via any connection method

A post-incident report has been published.

A post-incident report has been published.

Title: Some users may be unable to access Microsoft 365 Copilot Chat via any connection method User impact: Users may have been unable to access Microsoft 365 Copilot Chat via any connection method. More info: Impacted users may have experienced failed session loads, persistent errors, or unresponsive Copilot chats due to backend services being unable to initialize successfully. Final status: We've identified and reverted a recent configuration change that altered how user sign in requests were processed. We've now confirmed that impact has been resolved. Scope of impact: Impact was specific to users attempting to access Microsoft 365 Copilot Chat via any connection method. Start time: Thursday, May 14, 2026, at 1:40 AM UTC End time: Thursday, May 14, 2026, at 3:35 PM UTC Root cause: A recent configuration change to the authentication component altered how user sign in requests were processed. This introduced a mismatch in expected authentication behavior, causing authentication requests to fail. Next steps: We're examining our configuration change process so we can identify areas for process improvement in future deployments. A preliminary post incident report (PIR) Will be published within 2 business days from closure, and a final PIR will be published within 5 business days from closure.

We've identified and reverted a previous configuration change that appears to have affected an authentication workflow within the service. We're now observing recovery in service telemetry. This quick update is designed to give the latest information on this issue.

Title: Some users may be unable to access Microsoft 365 Copilot Chat via any connection method User impact: Users may be unable to access Microsoft 365 Copilot Chat via any connection method. Current status: We've identified a potentially impacting IP classification dataset version, which we're preparing to revert to a version prior to the suspected impacting change window to unblock ECS access as an initial mitigation. We're monitoring service telemetry and error logs to validate this and to help identify the root cause of impact. Scope of impact: Impact is specific to users attempting to access Microsoft 365 Copilot Chat via any connection method. Start time: Thursday, May 14, 2026, at 12:40 AM UTC Next update by: Thursday, May 14, 2026, at 5:00 PM UTC

Title: Some users may be unable to access Microsoft 365 Copilot Chat via any connection method User impact: Users may be unable to access Microsoft 365 Copilot Chat via any connection method. Current status: We’re reviewing service telemetry and recent service deployments to isolate the root cause of the issue and determine a fix. Scope of impact: Impact is specific to users attempting to access Microsoft 365 Copilot Chat via any connection method. Next update by: Thursday, May 14, 2026, at 3:00 PM UTC