The MCP portal can report that the sign-in cookie was not returned or that the sign-in form has changed. These messages concern the browser’s current sign-in form and session checks.
Allow cookies for the portal when your browser settings permit them, reopen Sign in, and enter the account credentials through the fresh form. Avoid repeatedly submitting an old tab whose form state may no longer match the session.
If you were connecting from an assistant, return through its connection flow after correcting the browser issue. Confirm the displayed assistant and company before approving access.
This error is not a request to share a cookie or session token with support. Describe the exact message and browser behavior without copying reusable authentication data. If normal sign-in still fails after reopening the form, check the account and authenticator requirements. The secure form checks should be resolved through the normal portal flow rather than bypassed with a manually edited authorization URL.
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