I actualy have the same problem. I'll contact Pretendo's Discord server to see if I can get help there. If I can get an answer I'll make a post about it in the Splatoon comunity.

This error is related to Spotpass. To fix it, download Nimble (30_nimble.rpx) and put it in this path on your SD card: wiiu > environments > aroma > modules > setup.

Thanks