Without any warning from Nintendo, the Wii and DSi shops have been offline for the past 3 days. The first found report of this realization was by a Twitter user named OatmealDome sharing pictures of both the shops showing error codes when trying to access them.
There are questions regarding it all as there has still yet to be a statement from Nintendo and the fact that there are no issues shared under Nintendo’s network status page. The Nintendo Wii shop closed up back in January 2019. It is currently impossible to download any purchases on either platform that is not already downloaded on your system.
The DSi shop closed back in September 2016, with many DSi digital titles being available on the Nintendo 3DS. However, that will soon change as the 3DS and Wii U eShop are closing their doors in March next year, making it impossible to purchase anything whether you have funds in your wallet or not.