You might not have used the Game - Set Next Level trigger at the end of the last level....or if you meant it's not loading when you click on the button on the campaign screen, you might not have loaded the map to the button (they have to be linked together, it's on the Loading Screen tab of the Campaign Editor).
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.