First confirm that your Zune Pass is up to date and still active, and if it is, make sure you are actively signed into Zune, and not using cached login credentials. Sign out of Zune, close the Zune client and any instances of Internet Explorer, then start Zune again and sign in, then sync.
Also, make sure you're signed into Zune with the right account! It's pretty frequent for computers used by family members to end up with similar issues, because people didn't realize their husband/wife/son/daughter/etc had signed in with their account. :)
Corey Snow
Zune Services Team
.:[This posting is provided "as-is" and confers no warranties or rights.]:.