I don't know the intricacies of why it works that way, but given the many threads on this forum and elsewhere, this is typically the case. Maybe because the crack was based upon a demo version, or the Abes find out which serial codes are being abused and lock them down.
Anyway, people using cracks is a reality of life and some people may eventually go legit and buy, in which case, it's not so bad, but while they are doing something illegal, you would think they'd be keeping a low profile and not brazenly admitting in that software company's official forum that they are running a ripped off version. That is just madness to me, and given how easy it is to trace these posts, I'm surprised that the Abes aren't doing more to track down the warez users and challenge them on it. They probably can't afford to do it because they can't hire the computer guy or legal aid to do it, because of the lost revenue from the amount of warez users who are too cheap to pay !!!!