Today, Nintendo has released a relatively minor update for the Switch and Switch Lite, bringing the version to 10.0.4. With this new version, Nintendo is addressing an issue with the Nintendo eShop which would make it very hard or sometimes impossible to add funds or register a new credit card to your account.
“We have fixed the issue where it was not possible in some countries or regions to add funds using a new credit card or to register credit card information in Nintendo eShop on Nintendo Switch.”
Version 10.0.2 came at the end of April and version 10.0.1 was a much smaller release with only very minor bug fixes. To update your Nintendo Switch, it can be done in the Settings section, but most consoles will update automatically.