["https://<server>[:port]"] or ["http://<server>[:port]"]
we are assuming server is our arcgis organisational landing page but what is the port?
Have you provided a valid ClientID (aka App ID) to the app in the advanced settings?
We have provided the app ID, but we are unsure about what the redirect uri is. Does it automatically provides the uri once the app ID is provided.
Can you please try using this "urn:ietf:wg:oauth:2.0:oob" for redirect_uri when registering your app in your org account?
I tried this and it worked out. thanks man.