Troubleshooting Missing Google OAuth2 Consent Screen in Self-Hosted n8n Setup

Below is a few troubleshooting suggestions based on the n8n documentation for setting up Google OAuth2 credentials:

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1. Verify Your Redirect URI

Make sure you’ve copied the exact OAuth Redirect URL from your n8n credential configuration and added it as an Authorized Redirect URI in the Google Cloud Console. Even minor mismatches (trailing slashes, http vs https differences, etc.) may cause the OAuth flow to behave unexpectedly.

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2. Check the OAuth Consent Screen

Double-check that the OAuth consent screen in your Google Cloud Console is fully configured. This includes:

• Setting the correct User Type (Internal vs. External)
• Adding your valid Authorized Domains (for example, if using n8n Cloud, ensure n8n.cloud is included; if self-hosted, add your domain)
• Ensuring required fields (App name, support email, developer contact) are properly filled

If these aren’t correct or if the app is still in a “Testing” state, it might lead to issues with the approval window.

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3. Confirm the OAuth Client Credentials

During the creation of your Google OAuth client credentials, ensure you selected Web application and updated the automatically generated Name (if needed) so that you can easily match it in the console. Then, verify that you’ve copied both the Client ID and Client Secret into your n8n credential.

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4. Scopes and Permissions

When finalizing your credential in n8n, remember to enter the required Google scopes as a space-separated list (for example, for Gmail):

https://www.googleapis.com/auth/gmail.labels https://www.googleapis.com/auth/gmail.addons.current.action.compose

If you enter any scopes that are either misconfigured or not supported, the expected OAuth consent window may not show up as expected.

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5. HTTPS and Environment Considerations

Google generally enforces strict security for OAuth flows. If your n8n instance is locally hosted with HTTP rather than HTTPS, that might cause issues with the consent flow. Verify whether you’re running on a secure host and that your domain configuration matches what you’ve set up in your OAuth consent screen.

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6. Downstream Repo Setup

Since you mentioned using a downstream repo (which includes additional components like OpenWebUI and Flowise) that might have been modified from the standard n8n configuration, it’s possible the modifications affect the OAuth flow. As a test, try setting up the OAuth credentials following the official n8n documentation in a clean environment (via Docker Compose based on the official docs) to see if that resolves the issue.

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Final Thoughts

It sounds like you might be dealing with a misconfiguration—most likely with the redirect URI or OAuth consent configuration. Re-check these elements against the official guides:

• Google OAuth2 Generic
• Google OAuth2 Single Service

Following the official documentation step-by-step should help ensure that Google's permission screen appears as expected. If the problem persists, consider testing in a more minimal n8n setup to rule out interactions introduced by the additional components in the downstream repo.

Feel free to ask for additional details on any of the steps!