Facebook Marketing API - adding ProductCatalog
What is the level of Ads API access that the app you use has? As described here there are different levels. Since Product Catalogs uses Business Manager, you need to have Marketing API Access with the "Standard" level.
If your app is still on "Development" or "Basic" access, see the above mentioned documentation to read how you can apply for higher access.
You can see what level of access you have by going to you App Dashboard --> "Status and Review", create a new submission for review and see which permissions are available.