Sorry for the inconvenience.
If this error is displayed, there is a possibility that it can be improved by using the following method, so please try it out.
- Clear your browser cache
There is a possibility that an error has occurred due to the effect that the previous cache remains.
Please close all browsers, clear your browser cache, and then try logging in again. - Update your password
There is a possibility that your password is incorrect.
Try updating your password on the NDID management page.
https://ndid.mng.nintendo.net/ndid/
If the above method does not resolve the issue, there is a possibility that the registration information is incomplete.
Please contact Nintendo Support with the NDID used to log in and the email address set to it.