same i cannot either its like servers are down.

go to settings and data and splatoon, then delete shared save data

install nimble and clear BOSS data if your Wii U is homebrewed

Kip is it on Homebrew App Store?

Download "30_nimble.rxp" and paste to "sd:\wiiu\environments\aroma\modules\setup\" Open Splatoon, restart console, open Splatoon again Error 118-0521 is for connecting to other consoles. Just keep trying.

Thanks everyone! It turns out I had forgotten to delete shared save data.