For some reason you have to do extra steps to get it to work, but only one time.
^ if you do this one you don't actually have to finish making a new injection, just follow the instructions to create a virtual memory card on the sd card. This is probably the easiest way. However, this is using the Wii U VC injector made by TeconMoon, not the UWUVCI AOI injector. So you would have to download that injector, also have your sd card in your computer so it can download the gamecube virtual memory card to the sd card.
Alternative: get an actual gamecube rom and enter Nintendont on vWii and enter settings and create a virtual memory card. You must then enter a game for it to save the settings this is why you need the Gamecube rom. You should only have to do this one time. After this when you start a new Gamecube game on the Wii U it should ask if you want to create a memory card you say yes, it creates a different memory card for each Gamecube game.