Problem connecting to some application on _think_ using oauth

Description of the problem

The error happens on some application using oauth or oidc. (like komga,Statping or argocd). The logging work if we are already login in authentik, but cannot login otherwise.
Accessing applications is redirecting to the login default page if/flow/default-authentication-flow/?next=%2F and then show an error in both UI and logs.

Steps to reproduce it

1. Open a browser in incognity
2. Visit https://read.thinkhead.org/
3. Click on sign in with authentik

Expected behavior

Supposed to correctly login and redirect to the content of the site.

Behavior detected

Show an error in authentik: ** Request has been denied**

Environment

• OS: All
• Browser: All

Additional context

GitHub issue opened

Imported from ThinkBugs (Astuto), originally posted 2024-06-20.