Microsoft 365 Alert – Service Degradation – Microsoft 365 suite – Some users may be unable to access Office.com or the Microsoft 365 Copilot web sign in page – RESOLVED

17/03/2026 08:37:00 AM

NHSmail Reference: INC46774657

Microsoft Reference: MO1253428

Issue Status: RESOLVED

Issue Description: Some users may be unable to access Office.com or the Microsoft 365 Copilot web sign‑in page.

More info: The impacted web-client was office.com, and impacted Microsoft 365 Copilot web-clients were office.com/chat, m365.cloud.microsoft, m365.cloud.microsoft/chat and copilot.cloud.microsoft.
Users could access Microsoft Copilot through application-based Microsoft Copilot services. This included but wasn’t limited to:
– Microsoft Copilot desktop app
– Copilot in Microsoft Teams
– Copilot in Office apps
User may have been able to leverage office.com/search, which redirects to https://m365.cloud.microsoft/search, and should’ve been able to sign in using this page. Once signed in, users could access the impacted web-based office.com and Copilot clients.

Final Update: 17/03/2026 08:37:00 AM –Microsoft has confirmed through our service-side telemetry that that the service health has fully recovered and impact has been successfully remediated.

Scope of impact: Impact was specific to some users who were served through the affected infrastructure.

Root cause: The infrastructure that supports access to Office.com and the Microsoft 365 Copilot web sign-in page received a high volume of traffic that inhibited the rate in which some users’ requests were being processed, preventing some users from accessing the service pages.

Next steps: Microsoft are continuing to monitor the affected infrastructure closely to ensure the service remains stable and to help inform any changes we can make to improve the service’s resilience against similar issues in the future.