Error calling token exchange endpoint using Postman


I’m testing out the using postman (using grant_type: authoriation_code) and am getting the following error when I make the call to get the token:
“error”: “invalid_client”,
“error_uri”: “”,
“error_description”: “The client_id and client_secret must authorize the app.”

I’ve registered my app, authorized it, and am using the code, client_id, client_secret from the app. Is there something else I may have missed?