When connecting Google Drive, Gmail, Google Sheets, or another Google API to n8n, you may see an Access blocked message saying the app has not completed the Google verification process. This usually happens when your Google Cloud OAuth app is still in testing and the Gmail account you are using has not been added as an approved test user.
If you are also working through self-hosted node errors, the previous guide explains how to fix the n8n MCP Client Tool unrecognized node type issue. This article focuses only on the Google OAuth access blocked flow.
Why Google Blocks the Connection
Google Cloud apps in testing mode can only be authorized by approved test users. If your n8n OAuth credential requests Drive or other Google scopes and your Gmail account is not listed as a tester, Google blocks the authorization before n8n can finish connecting the account.
Step 1: Create the Google Credential in n8n
Open your Google Drive node, choose the trigger or action you need, and create a new OAuth2 credential. n8n will show a redirect URI. Keep this page open because you need that URI in Google Cloud.
Step 2: Create or Edit the OAuth Client in Google Cloud
In Google Cloud Console, open your project and go to APIs and Services > Credentials. Create an OAuth Client ID with application type set to Web application. Paste the redirect URI from n8n into Authorized redirect URIs, then save.
Copy the Client ID and Client Secret from Google Cloud back into the n8n credential fields and save the credential.
Step 3: Confirm the Access Blocked Error
If the Gmail account is not yet approved as a tester, clicking Sign in with Google will lead to the access blocked page. The important clue is the message that the app is being tested and can only be accessed by developer-approved testers.
Step 4: Add the Gmail Account as a Test User
Go back to Google Cloud and open the Google Auth Platform or OAuth consent screen area. Then open Audience and find Test users. Add the exact Gmail account you are trying to connect in n8n, then save the change.
Use the same email address: if the n8n popup is trying to authorize one Gmail account but you add a different email as the test user, the access blocked error will continue.
Step 5: Try the Google Sign-In Again
Return to n8n and click Sign in with Google again. You may now see a warning that Google has not verified the app. For a private test app you created yourself, continue only if you recognize the app and understand the scopes it is requesting.
Step 6: Confirm the Account Is Connected
After continuing through the Google consent screen, n8n should show the credential as connected. You can then choose the Google Drive folder, fetch a test event, or continue configuring the Google node.
Troubleshooting Checklist
- Make sure you added the same Gmail account that appears in the Google authorization popup.
- Confirm the OAuth client belongs to the same Google Cloud project as the OAuth consent screen you edited.
- Check that the n8n redirect URI exactly matches the Authorized redirect URI in Google Cloud.
- If you changed Client ID or Client Secret, save the n8n credential again before retrying.
- If the OAuth app is in testing mode, remember Google limits testing apps to approved test users.
- If you need access for many outside users, you may need to publish the app and complete Google verification instead of relying on test users.
Final Thoughts
The fastest fix for the n8n Google verification access blocked error is usually not to rebuild the credential. Add the Gmail account as a Google Cloud test user, confirm the redirect URI, reconnect from n8n, and then test the Google node again.
References
Official references used for accuracy: Google Cloud Manage App Audience documentation, Google Cloud OAuth app branding documentation, and n8n Google OAuth single service credential documentation.
Olaitan Oladipo holds a BSc in Sociology from Olabisi Onabanjo University. He is a self-taught automation builder who has spent years inside n8n doing the work that most tutorials skip: debugging OAuth errors at 2am, migrating client automations from Make.com mid-project, fighting reverse proxy misconfigurations on AWS EC2, and figuring out through trial and error what actually holds up in production versus what only looks clean in a demo.
He is not a developer by training and not a SaaS founder. He is the person in the Discord server who actually answers the question instead of linking to the docs.
His writing on n8n Automation Tutorial covers self-hosting, AI agent workflows, tool comparisons, and the security vulnerabilities the automation industry would rather not discuss. He has built AI-assisted invoice approval flows using OpenAI function calling, connected Claude via HTTP Request nodes, and holds considered opinions about Zapier, Make.com, LangChain, and CrewAI that their marketing teams would not appreciate.
He writes for people who are technical enough to follow a tutorial but experienced enough to want the honest version.