Nginx reverse proxy shows 502 for Keycloak registration form submission

Keycloak is amazing and one by one I have solved problems through reading documentation (which is extremely hard to be honest) and through getting help from the community.

I have this setup:

  1. Nginx as the reverse proxy
  2. Docker as the Keycloak’s standalone instance

Almost everything works, including roles and access to my API (which is .NET Core) and securing my Web app (which is React).

However, when user wants to register, on form submission I see 502 error in nginx.

You can check it out here:

https://accounts.freya.center/auth/realms/Development/protocol/openid-connect/registrations?client_id=UserPanel&response_type=code&scope=openid%20email&redirect_uri=https://user.freya.local/tickets&kc_locale=en

How should I fix it?

Thank you