You open a Microsoft 365 desktop app like Word or Outlook and attempt to use Copilot, only to see the error MSAL_ERROR_INVALID_REFRESH_TOKEN. This error prevents Copilot from generating responses or connecting to Microsoft Graph data. The cause is a corrupted or expired refresh token that the Microsoft Authentication Library MSAL can no longer validate. This … Read more
When Copilot fails to authenticate, you may see an error referencing a PKCE code verifier mismatch. This occurs when the cryptographic challenge sent by your client application does not match the verifier expected by the Microsoft identity platform. The mismatch blocks the token exchange and prevents Copilot from accessing Microsoft 365 data. This article explains … Read more
When using Copilot on a domain-joined Windows PC, you may see an error message stating that the Kerberos ticket has expired. This error typically occurs during a Copilot session when the underlying authentication token used by Microsoft 365 services is no longer valid. The root cause is that the Kerberos ticket granted by your domain … Read more
When you try to use Copilot in Microsoft 365 apps or on Windows, you may see the error message “WinHTTP Error 12175” followed by “Certificate Revocation Check Failure.” This error prevents Copilot from connecting to Microsoft servers, blocking chat, drafting, and summarization features. The cause is a local system setting that disables or interferes with … 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 The cause is often a corrupted add-in registration, a damaged Word startup state, or an outdated Microsoft 365 installation.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
When you use Copilot inside Microsoft 365 apps on a corporate network, you may see the error message “Self-Signed Certificate in Chain.” This error stops Copilot from generating responses or connecting to the Microsoft Graph. The root cause is a corporate proxy or network security appliance that intercepts HTTPS traffic and replaces Microsoft’s certificate with … 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