Did you put “DEVICE_AUTH_URL_123”, “CLIENT_ID_123” and “AUDIENCE_URL_123” in your Postman request like that just for the example ? Because device auth url and client id you put in your Curl are variables, but don’t seem to be such in Postman.
Also, have you ensured your application in Auth0 has device code grant type enabled ?
Edit : I just noticed something : you put client id, scope and audience as parameters, but you have to add these in the body, in “x-www-form-urlencoded” !
Have you tried putting client_id, scope and audience in the request body like I asked in my post edit ? I noticed you had put these as parameters before, but I think the API is waiting for a body.