Microsoft 365 Alert – Service Degradation – Microsoft 365 Copilot Chat – Users may have been unable to access Microsoft 365 Copilot Chat via any connection method – RESOLVED

15/03/2026 09:08:00 AM

NHSmail Reference: INC46827112

Microsoft Reference: CW1310341

Issue Status: RESOLVED

Issue Description: 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 Update: 15/05/2026 09:08:00 AM –Microsoft has identified and reverted a recent configuration change that altered how user sign in requests were processed. They have 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.

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 update by: Microsoft are examining their configuration change process so they can identify areas for process improvement in future deployments.