When using Copilot in Microsoft 365, you may encounter a 407 Proxy Authentication Required error. This error prevents Copilot from connecting to Microsoft services through your corporate proxy server. The 407 status code means the proxy server requires authentication before it will forward requests to the internet.
This error typically occurs in enterprise environments where all outbound traffic must pass through a proxy server configured with authentication. Copilot and the underlying Microsoft 365 services fail to send the required credentials to the proxy. As a result, the connection is blocked and the 407 error appears in the Copilot pane or in the browser console.
This article explains the root cause of the 407 error with Copilot and provides step-by-step fixes. You will learn how to configure proxy settings in Windows, update Microsoft 365 apps, and adjust network policies so Copilot can authenticate through your proxy server.