[Wii] I cannot register with friends

[Guernsey]

Can anyone tell me why I cannot register people? I have the Wii numbers of most of my friends for some games as well as their Wiis yet for some reason it won't register them. I know they are supposed to register me as well as them and I did gave them my code but I don't if they got through or if I got through to them. Is there something wrong? I wanted to register people but something isn't working here.