AuthorizationCode flow working using browser but not using Postman

Question

I have an Authentication Server application (AuthServer) using OpenIdDict. And a client application (ClientApp) which has a simple controller action:

Startup client configuration:

builder.Services
 .AddAuthentication(o => { o.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme; })
 .AddCookie()
 .AddOAuth("OpenIddict.Server.AspNetCore", o => { 
 o.AuthorizationEndpoint = new Uri($"{AuthenticationServerUrl}connect/authorize").AbsoluteUri;
 o.TokenEndpoint = new Uri($"{AuthenticationServerUrl}connect/token").AbsoluteUri;
 o.ClientId = "testoauth";
 o.ClientSecret = "testsecret";
 o.CallbackPath = new PathString("/callback/login/local");
 o.UsePkce = true;
 });

The client controller action:

[HttpGet("oauth")]
[Authorize(AuthenticationSchemes = "OpenIddict.Server.AspNetCore")]
public IActionResult OAuth2() => Ok($"Successfully authorized with authorizationcode flow.");

I think it has something todo with the cookie: ".AspNetCore.Identity.Application". It is not created somehow using Postman. I see that the Cookie is created in the browser dev-tools. Postman generates the access_token successfully. But is not added to the cookies collection.

Fix: After creation of the access_token, Postman is not added this cookie to the request header. It can be found in the Console section of Postman, so add it manually. Do the request again and the action will be called.

• Tiny Wang: May I know what is your problem now? Or what trapped you?
• Christiaan: @TinyWang Never mind, I found my answer. The issue was that the .AspNetCore.Identity.Application cookie was not automatically added to the Postman cookies. So I manually added the cookie to the Postman cookies collection. This cookie can be found in the Postman console when generating the access_token.
• EJoshuaS - Stand with Ukraine: Please post the fix as an answer - don't edit it into the question itself.