I have created a public app in Partner Dashboard and created a test store
I am running postman hitting endpoint "admin/oauth/authorize" by passing client_id, scope & redirect_uri. In the response I am getting code as a querystring. I took that "code" value and hitting endpoint "admin/oauth/access_token/" with client_id,client_secret & code through postman.
I am getting the below error
Oauth error invalid_request: Could not find Shopify API application with api_key