CX App product fields inside App Configuration in Program (Service related endpoints)

We are developing a cx app and we are currently working on the Service Configuration endpoints.

However, we are unable to retrieve the product information (fields/columns) using window.parent.postMessage (amsAction = "product"), returns 403 (Forbidden).

The metadata call (amsAction = "metadata") works normally.

There's two calls, one for metadata (working) and one for product (403 forbidden).

I tried to change the app's permissions on AMS. I added all the (readable) options available, without success.