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This article covers OAuth sign-in issues that affect listed MCP clients such as Claude, ChatGPT, Cursor, and VS Code. If you are using an unlisted MCP client with a connection token, you do not use the browser sign-in flow. Go to the Unlisted MCP client tab instead. When you sign in to Zapier MCP through your browser, the sign-in window may complete successfully but your MCP client never receives the result. This typically happens with terminal-based MCP clients, certain WSL configurations, or browser extensions that interfere with sign-in redirects.

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Symptom

The sign-in window opens in your browser and appears to finish successfully, but your MCP client never receives the result and the connection does not complete.

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Causes

  • Claude Code is running on WSL (Windows Subsystem for Linux) and the sign-in redirect cannot reach the MCP client.
  • VS Code extensions are interfering with the sign-in process.
  • A terminal-based MCP client cannot receive the sign-in result back from the browser.
  • An older version of Cursor or Windsurf has a known sign-in bug that prevents the connection from completing.
  • Claude Desktop did not pick up the completed sign-in.

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How to fix it

Try one or more of the following:
  • Start the sign-in from inside your MCP client and wait for it to prompt you to open your browser.
  • Do not open the sign-in link before your MCP client is ready to receive the result.
  • Check that your browser is not blocking pop-ups or redirects from zapier.com.
  • Update your MCP client to the latest version.
  • Use a different browser. Some browser extensions can interfere with sign-in redirects.
  • Restart your MCP client (especially Claude Desktop) and try connecting again.
OAuth redirects cannot reach Claude Code when it is running inside WSL. Run your MCP client from a native Windows terminal instead of a WSL terminal, then try connecting again.
Extensions can intercept the OAuth redirect before VS Code receives it. Disable your extensions and try connecting again. If the connection succeeds, re-enable extensions one at a time to identify the conflict.
If your MCP client does not support OAuth, regenerate your connection token and set up the connection again from scratch using the new server URL.

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Last modified on September 8, 2026