Highlevel Oauth2 API

Questions
1

Describe the problem/error/question

I’m encountering an issue when setting up an OAuth2 integration with GoHighLevel in n8n.

The authentication flow does not complete because the login window fails to actually log in the user. The popup redirects to the GoHighLevel login screen, but after clicking “Login”, nothing happens. The user is not authenticated, and the OAuth process does not proceed.

This issue does not occur when I manually paste the authorization URL in a normal browser tab. It only happens within the popup window triggered by n8n when clicking “Connect” in the credentials panel.

What is the error message (if any)?

There’s no explicit error, but the OAuth popup displays the following message:

“Please login to HighLevel to continue”

(even if I’m already logged in)

Clicking the Login button reloads the same page without progressing.

Please share your workflow

Please share your workflow

OAuth2 credential created with the following values:
	•	Auth URL: https://marketplace.gohighlevel.com/oauth/authorize
	•	Token URL: https://marketplace.gohighlevel.com/oauth/token
	•	Client ID / Secret: (valid and verified)
	•	Redirect URI: https://oauth.n8n.cloud/oauth2/callback
	•	Scope: (long but valid list, also tested with basic ones like contacts.readonly contacts.write)
	•	Grant Type: Authorization Code
	•	Authentication Method: Header

Manually opening the auth URL works fine and I can retrieve the code, but the popup from n8n is unable to maintain the session/login state.

## Share the output returned by the last node
Not applicable – issue occurs during credential setup, not during workflow execution.

OAuth popup should correctly retain the session and allow GoHighLevel login to complete. After logging in and choosing a location, it should redirect back to n8n with the code parameter.
2

A lot of the issues with Oauth2 are related to missing a step in setting up the app when you create the client id / client secret.

The first thing to do is double check that you have done step 3 in the HighLevel credentials setup instructions.

3

Yes, I can confirm that step 3 in the HighLevel credentials setup was completed correctly .

In fact, when I manually open the authorization URL in a regular browser tab (outside of n8n), everything works as expected — I can log in, select a location, and obtain the authorization code successfully.

The issue specifically occurs within the OAuth popup window that n8n opens when I click “Connect” in the credentials panel. In that popup, the login to HighLevel doesn’t work: clicking the login button reloads the same screen without authenticating the user. It’s likely related to session or cookie handling in the embedded window.

So to clarify: the OAuth flow works perfectly in the browser , but fails when triggered via n8n’s built-in popup interface .

4

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