In order to fix this problem, there are some things that you can try. You can test your Internet connection. To do that, select the Home button -> select the Wrench icon -> Open -> Internet Settings -> Connection Settings -> select your connection and select Connection Test. If the connection test succeeds you have a working Internet connection and you need to contact the developer of Netflix on the following website. If it fails, you need to visit the Nintendo's support website for further assistance.
You can also check to see if the date and time is properly set on your device. For more information regarding this problem, you can visit the following official website.