The Nintendo Wii and DSi stores have been down for days with no explanation

engadget.com:

Nintendo stopped selling DSi and Wii games in 2017 and 2019 respectively, but it has continued to allow users to download games they already own. Now, both stores have gone completely offline with no explanation from the company, Eurogamer has reported. If you try to select the Wii Shop channel, you'll just see a blank white screen and error code — a situation that has persisted for around four days.

When it initially shuttered those stores, Nintendo said that you'd still be able to download purchased games for an unspecified period of time. However, it warned that the servers would eventually be shut down completely, meaning folks wouldn't be able to download or transfer purchased games using the Wii System Transfer Tool.

Nintendo has kept these stores running for a long time (since 2006 in the case of the Wii), but folks would rightfully be upset if Nintendo shut off access with no heads up whatsoever. Many would no doubt have liked at least a few months notice so they could download or transfer their games. The servers do appear to still be up, though, as some folks have found they can use third-party tools like NUSDownloader to access games. 

Sony was recently forced to backtrack on a decision to close the PS3 and Vita stores after a consumer backlash. The situation isn't quite same for Nintendo, but it should probably provide some kind of explanation if the stores don't come back online soon.