Minecraft wiki entry for Playing_on_servers, associated text: If Minecraft updated recently, you might get these error messages. They mean that you are running a different version than the server. You can only connect to servers with the same protocol version as your client. You can create a new profile in the launcher with the version the server is running or you will have to wait for the server to update, that may take more or less time depending of the server owners' reactivity.