SkyTeam lounge access rules only apply to lounges operated by SkyTeam or a SkyTeam-member airline.
If a third party is responsible for providing lounge access to a particular SkyTeam airline in whose FFP you don't have lounge-access status, you should ask for a lounge pass at check in at the airport (and there's no guarantee that you'll get one). When third parties are providing the lounge, it's usually intended ONLY for status members of that particular airline's FFP as a service only for that airline's customers, but NOT as a full SkyTeam benefit.