I match issue

I already downloaded I match to my pc but cannot switch my iPad over. My computer, pc says I have over 6000 songs available but when I go to settings on ipad and select music then try to slide I match bar on, It keeps saying I need to subscribe but I already paid using my pc and my pc , iPad and two other computers are all registered under the same apple Id. I checked. Any ideas? I have read a few articles on subject and can't figure it out.