OAuth2.0 Redirect does not happen (Single-Sign-On)

[Trickfilm400]

Hi,
I have a route on an express which is protected via OpenID Connect (so OAuth2)
The Express-Backend is using a session-based Single-Sign-On (The backend creates a Session after the SSO redirect back to the backend after the login on the SSO page)

In the webbrowser everything is working - I can login and have a session cookie and I am authenticated.

But with insomnia, I dont get a session cookie - the request to the backend just dont happen.
In the Response Timeline of the Access token, only the request to the token endpoint (> POST /oauth/v2/token HTTP/2) is mentioned.

But in the developer console there it says Detected redirect https://callback-uri/?code=[...] (which would be the correct way like in the webbrowser)
But this request does not happen, not in the timeline of the OAuth session nor am I able to find this in the backend

So the question:

• Why is this request back to the backend to the redirect uri not happening? Is this not the intended way of OAuth2 or is some configuration or anything else broken?
• -> Can Insomnia handle session-based OIDC requests?

Some details:

• used test example project for SSO: https://github.com/goranlisak/openid-connect-sample
• SSO Provider tried: Zitadel, Keycloak
• Also tried with postman - same issue

[KayleeTheMech]

Same Issue. Setup is Keycloak as identity provider and a scala backend.

Keycloak's error is: "Cookie not found. Please make sure cookies are enabled in your browser." With a regular browser I'm able to access the API.