Fixing the “Connection Failed” or “Unauthorized (401/403)” Error in n8n – A Step-by-Step SOP Guide

Ever hit a “Connection Failed” or “Unauthorized (401/403)” error while building your dream automation in n8n?

You’re not alone – it’s one of the most common roadblocks users face while connecting APIs like Google Sheets, OpenAI, or Notion. But the good news? It’s also one of the easiest to fix once you understand the root cause.

In this post, we’ll walk through a clear SOP-style guide to diagnose and resolve this issue – step by step. By the end, you’ll know exactly what causes the 401 or 403 errors and how to prevent them from breaking your workflows again.

🧩 Understanding the “Unauthorized” Error in n8n

Before fixing it, let’s decode what’s really happening.

When n8n throws an Unauthorized (401) or Forbidden (403) error, it’s saying:

“Hey, I tried to talk to the external app, but I wasn’t allowed in!”

This usually happens when:

• Your API credentials (token or key) are missing, expired, or incorrect.
• The scope or permission on your API key doesn’t match what you’re trying to do.
• You’re using a wrong authentication method (like Basic Auth instead of OAuth2).
• Or your account IP or app access is restricted by the external service.

⚙️ SOP: Step-by-Step Resolution Guide

Here’s a structured Standard Operating Procedure (SOP) to fix the “Connection Failed” or “Unauthorized” (401/403) errors in n8n.

Step 1: Identify the Exact Error Source

1. Open your n8n workflow editor.
2. Run the node that failed.
3. Look at the Execution log → Error details.
   • Example message: ERROR: 401 - Unauthorized: Invalid API key or token.
4. Note the node name (e.g., HTTP Request, Google Sheets, or Notion) and service it connects to.

🧠 Tip: The “node type” will help you know which credentials or tokens to check later.

Step 2: Check API Credentials in n8n

1. Go to Credentials in your n8n dashboard (⚙️ Settings → Credentials).
2. Find the credentials linked to the failed node.
3. Click Edit → and check:
   • Is the API key or token still valid?
   • Does it match the one on your third-party account (like Notion or OpenAI)?
   • Was it generated for the correct environment (production vs. test)?

🔑 Example:
If your OpenAI node fails with a 401, recheck your key in OpenAI API Keys.

If it shows “Expired” or “Revoked,” create a new key and update it in n8n.

Step 3: Verify Authentication Type

Different services use different authentication models. Using the wrong one can instantly trigger 401 or 403 errors.

Here’s a quick guide:

🛠️ Fix:

• Go to your node configuration.
• Under Authentication, ensure the correct method (OAuth2, Basic Auth, etc.) is selected.
• Reconnect your account if required.

Step 4: Test Your Token Outside n8n

To isolate the problem, test your API key manually.

• Open a tool like Postman or cURL.
• Send a simple request using your token. Example for OpenAI: curl https://api.openai.com/v1/models \ -H "Authorization: Bearer YOUR_API_KEY"
• If it fails outside n8n too – your token is invalid or expired.

💡 If it works in Postman but fails in n8n, your node configuration likely has a wrong header or variable format.

Step 5: Reauthorize or Regenerate Access

If you’re using OAuth2 (like Google, Notion, or Slack):

1. Go to your connected app’s dashboard.
2. Revoke the existing token.
3. Back in n8n, click Reconnect Account.
4. Reauthenticate and allow all requested permissions.

🔄 This refreshes your token and re-establishes the secure connection.

Step 6: Check API Permissions and Scopes

403 (Forbidden) errors often mean the token is valid but lacks access to what you’re trying to do.

Example:

• Your Google Sheets token allows read access but not write access.
• Your Notion integration doesn’t have permission to access a specific page.

✅ Fix:

• Open the connected app (e.g., Google Cloud Console or Notion Integrations).
• Add or adjust permissions to include read/write or full access.
• Then reauthorize your connection in n8n.

Step 7: Update or Recreate Your Credential Node

Sometimes, old credentials in n8n become corrupted or cached.

🧹 Quick Fix:

1. Delete the existing credential.
2. Create a new one from scratch.
3. Reconnect it to the affected node.
4. Save and test your workflow again.

Step 8: Rerun and Monitor

After all fixes:

1. Save your workflow.
2. Click Execute Workflow.
3. Watch the Execution Log – if it succeeds, your fix worked!

If you still get a 401/403, review your request headers or body formatting — sometimes missing a small JSON field can break authentication.

🧠 Pro Tip: Prevent Future n8n 401 Errors

• Schedule a token refresh every 30–60 days (especially for OAuth2).
• Use environment variables to store credentials securely.
• Always test APIs manually before adding them to n8n.
• Check out n8n’s official docs for integration-specific setups.

🔗 Useful Resources

• n8n Official Documentation
• FixMyAI.in Blog – learn more about automation and AI troubleshooting

🏁 Conclusion

The “Connection Failed” or “Unauthorized (401/403)” error in n8n can look intimidating at first – but once you follow these SOP steps, it becomes easy to fix.
Most of the time, it’s just an expired token or mismatched permissions. A few quick checks can save hours of debugging.

👉 Follow FixMyAI.in for more AI automation tips and troubleshooting guides!