Let me try to make some sense out of this for you, grrr. Others are welcome to help me out too.
Casinos come up with no deposit offers. The affiliate program for the casino makes the offer available to all of their affiliates. And when I say "all of their affiliates" that can equal a ton of affiliates. You will see the same offer on many, many different gambling sites.
While working with a casino affiliate program, affiliates will ask for or managers will offer exclusive bonuses. "Exclusive" meaning that only players who download from that specific affiliate's site can claim the bonus. If you are being denied a bonus, it is possible that you have clicked on a link somewhere to that casino which then "tagged" you to that specific affiliate. So if you found a better bonus for the same casino on a different site, downloaded, registered and then was denied the bonus, it's possibly because you were already tagged to the first affiliates link. We urge members on NDF to clear their cookies before clicking on our link to download from so you get tagged to us.
Now if you are being denied a "generic" bonus that everyone is offering on many different sites, I don't have the answer for that. There should be no reason why other than your bonus banned at that casino or something like that.
I am not sure I answered your question and if not, please explain further.