What upgrade?
What do you mean doesn't work?
What message so you get?
I see from your profile that you purchased 500 user license on 2009-10-29.
This initial purchase includes a one year maintenance period which expired on 2010-10-29.
Looks like you need to purchase a 1-year maintenance period extension to bring maintenance period to 2011-10-09.
Please see this post for instructions:
www.joomlapolis.com/forum/87-presales/163914-cbsubs-license-and-maintenance-periods