Apologies for the delay and I might need some more information.
Is the error happening when calling the API or when creating/editing the integration in the Developer Console?
When creating the integration, one (or multiple) product profiles need to be specified and they narrow down the API functionality. A developer needs to have been granted explicit access to those product profiles to call the API - that's what you might be running into.
If your question is more around Smart Content API functionality, I'd recommend the Adobe Experience Manager Asset Community which can be found here