"We have temporarily disabled the ability to participate in Rating Battles in Pokémon X and Pokémon Y.
If you try to participate in Rating Battles in your game, you should receive the following error code: 004-3003

Please continue to check the Pokémon Global Link and the official Pokémon website for updates about when Rating Battles will be available again. We apologize for the inconvenience."

Source: Pokémon Global Link