Forum Moderators: open
Second, remember that SEs treat your subdomains as if they are any other domain. Do you treat them like that? Do they have their own navigation systems, their own marketing, their own incoming links?
Lots of possible reasons for non-appearance.
You do not say how old the subdomains are; maybe they just haven't settled down yet?
If they are more than a few months old, you need to consider the possibility of a penalty; are you doing anything you shouldn't? For example, link exchanges with suspect sites?