Access Denied: The app could not be authenticated or is not authorized to query licenses of this Product ID.

I am trying to add licensing to my app. When I call:

ClientResult<AppLicenseCollection> licenseCollection = Microsoft.SharePoint.Client.Utilities.Utility.GetAppLicenseInformation(clientContext, productId);
            clientContext.Load(clientContext.Web);
            clientContext.ExecuteQuery();

this results in:

I have added both a license and the app to my sharepoint site.

Any idea what could be happening?

Thanks!