How come I cannot see my data when calling the API in the developer portal?
To communicate with the API, you need to identify your application. This is possible by using your client id and client secret1. These are linked to an account to make sure data from one account cannot be accessed by another account.
When using the API developer portal and its built-in client id and client secret, you are connected to the account linked to the API developer portal client. This means you can only access data created in the API developer portal.
1 See client credentials.