But am not able to clearly see console logs that indicate what happens wrong. No logs available or I am looking into wrong console? I also checked the devtools (current shell) console from blank popup. I was able to see some errors when my configuration had wrong urls, then fixed them.
I have just tried with Postman 9 on Mac and I am not facing this issue. Getting an access token using Authorization Code Grant type works fine.
I configured the same parameters (in Postman) than what you are showing in your screenshot above (for Authorization Code Grant Type).
Make sure to leave Scope parameter empty.
I assume that you environment variable is properly set (Postman environment variables).
Otherwise you can change the Auth URL and Access Token URL setting the proper region -> e.g. https://login.mypurecloud.de/oauth/authorize
The blank popup screen you are seeing after clicking on Get New Access Token should display the login web page for Genesys Cloud.
On Mac and with Chrome, I didn't get your issue - I mean I see the login screen.
I have found this post on postman forum and the description looks similar to yours: Blank screen when I request new access token - Help - Postman
You could possibly try the url mentioned in that post (and add it to your OAuth Authorization Code client in the Authorized Redirect URIs).
Otherwise, you can indeed use API Explorer.
API Explorer will get an access token using Token Implicit Grant type (no need to define an OAuth client in your Genesys Cloud environment).
So you will be able to issue API requests on behalf of the logged in user.
With Postman, you can also leverage Client Credentials Grant type.
Create an OAuth client in your Genesys Cloud configuration using this grant type.
In Postman, select the "Client Credentials" entry in the Grant Type drop-down.
Client Credentials token are usually used for a server/backend code that needs to connect to Genesys Cloud (not linked to a user context/account).
