google voice setup problem

[4wheelfurry]

I am having trouble setting up my voice mail so that it goes to google voice. I tried the *28 pluss my google # and it says invalid code. So I called the sprint tec and they set it up on their end but now when I call my cell it rings until voice mail is supposed to pick up but instead it says "we're having trouble completing your call..."
I double and tripple checked my # which is correct, is this a problem on Sprints end or Googles end or my end??? I have to get this figured out as I've already missed one very important call already!!