Here you go:
If I unselect the conditional, the ad works forum-wide. When I select the conditional as check-marked in the image the ad does not appear in the selected forum section.
I have tried researching this, and it appears I'm not the only one with an issue and that this is a bug. I just want to know if anyone has figured out a way around it.
I have tried disabling all other site ads to ensure it wasn't conflicting with anything else. But this made no difference.