Google Play Android Developer API - list entitlements - "Insufficient Permission"

When trying to list entitlements am getting:

 403 Forbidden                                                                                             

{
 "code" : 403,
 "errors" : [ {
 "domain" : "global",
 "message" : "Insufficient Permission",
 "reason" : "insufficientPermissions"
} ],
"message" : "Insufficient Permission"
}

I am using "WithInstalledApplication" authorization with client_secrets json.

IMPORTANT: Any other listing is working correctly (apks, inappproducts, ... ). Am only having this issue with the entitlements.

I am also sure my source code is correct, but just for the reference:

final AndroidPublisher service = AndroidPublisherHelper.init(appName, null);
final AndroidPublisher.Entitlements entitlements = service.entitlements();

EntitlementsListResponse entList = entitlements.list(pkgName).execute();
System.out.println("Entiltments: " + entList.toString());

Thank you for your suggestions.