I am not 100% sure about this but what I know this could just mean that that the DS could just be out of range from the access point. Or,since the DS needs some sort of network to connect to, have you changed your broadband recently?
Other possibilities include that you have not fully set up your new DS yet and you need to fully configure your settings. Or perhaps parental controls were put in place to stop Wi-Fi from working. Maybe the DS is faulty. Try and see the actual website to figure out what could of happened.