If you are using iOS, the issue may be solved by doing the following:
- On your device, go to Settings > Safari and select Clear History and Website Data
*Please note that browsing history, cookies, and other browser data will be deleted when you do this.
If you are accessing your Nintendo Account using a browser other than Safari, you can also try clearing the browser history or web data for that browser as well.
If you are having trouble registering your Nintendo account or have any issues with logging in or other areas, visit http://support.nintendo.com/ and select My Nintendo for further assistance.