Official documentation checked October 14, 2026. If a desktop Copilot experience reports an invalid refresh token or an MSAL sign-in error, first capture the actual error details and try the app’s normal interactive sign-in. The message does not establish that Windows Credential Manager is corrupt. A token may no longer be usable after a legitimate … Read more
Official documentation checked October 14, 2026. A PKCE mismatch is a failure in an application’s sign-in transaction, not evidence that you need broader SharePoint permissions. Microsoft Entra errors AADSTS50148 and AADSTS501481 identify a verifier that does not match the challenge associated with the authorization request. Microsoft’s error-code reference directs this problem to the application owner. … Read more
Official documentation checked October 14, 2026. A Kerberos error during Copilot sign-in on a domain PC needs to be traced to the authentication step that failed. It does not mean Copilot normally uses your computer’s Kerberos ticket to read Microsoft 365 content. Start with the full error code and corporate sign-in configuration, not a SYSTEM … Read more
Official documentation checked October 14, 2026. WinHTTP error 12175 means that Windows found a problem with the server’s TLS certificate. It does not, on its own, identify a failed revocation check or prove a Copilot-specific defect. Do not delete trusted roots, disable certificate validation, or remove security updates to make the connection succeed. 1. Identify … Read more
When you open Microsoft Word, the Copilot add-in may fail to load and display COM error 0x80004005. This error indicates an unspecified failure in the Component Object Model layer that prevents the add-in from initializing. The cause is often a corrupted add-in registration, a damaged Word startup state, or an outdated Microsoft 365 installation. This … Read more
Official documentation checked October 14, 2026. A self-signed-certificate or untrusted-chain error means the client could not establish the required certificate trust. A corporate inspection proxy is one possible cause, but the error is not proof that every certificate shown should be trusted. Identify the Copilot product, client, and certificate issuer before changing a trust store. … Read more
When you try to sign in to Copilot in Microsoft 365, you may see an error message that reads AADSTS500011: The resource principal named was not found in the tenant. This error means Azure Active Directory cannot locate the service principal for the Copilot application in your tenant. The root cause is usually a missing … Read more
When you open Copilot in Safari on a Mac, the sidebar may appear blank with no content, no chat input field, and no error message. This occurs because Safari’s default privacy settings block cross-site cookies and local storage that Copilot requires to load its interface. This article explains why the sidebar stays empty and provides … Read more
When you try to sign in to Copilot in Microsoft 365, you might see the error AADSTS500133: Assertion not valid yet. This error means the security token your device sent to Microsoft Entra ID was created with a time stamp that is before the current server time. The cause is almost always a clock mismatch … Read more
You open Copilot in Firefox Mobile’s Webview, type a prompt, and tap Submit. The page freezes, reloads, or closes entirely. This crash happens because Firefox Mobile’s Webview engine handles certain WebSocket and service-worker connections differently than Chromium-based browsers. This article explains the root cause and provides three working fixes you can apply now. Key Takeaways: … Read more