i have it set up.. set it up yesterday... maybe you put in the wrong phone number?.. i did jsut set it up to take care of my voicemail.. so i kept my old phone number it just forwards voice mail calls to the google voice mail part...
i set mine up all through the web page (voice.google.com) before i ever installed the app on my phone... at one point i had to type in a *400#something string into the phone so it knew what numebr to forward my voice mail to.. but if your using a number they gave you i'm not sure how it would work...