Authenticating in OAuth 2.0 Invalid redirect_uri.

I use Postman to try to log in to my Aras server, following the steps:
https://aras.com/en/blog/authenticating-in-oauth-2-0-with-aras-restful-api

But I get an Invalid redirect_uri error. While I can log in to the Aras server using: localhost/.../

Here is my Postman configuration:
Callback URL: localhost/.../PopupCallback
Auth URL: localhost/.../authorize
Access Token URL: localhost/.../token
Client ID: IOMApp
Scope: openid Innovator offline_access

Can someone please point me in the right direction on this?

Thanks