Can't watch HBO Free Preview

I have Cox Contour service with a CableCard and I am unable to access the HBO Free Preview.  I haven't tried re-scanning channels yet or re-adding the HBO channel in my Guide, but I can't even see it on Contour, which makes no sense at all.  Why can't I see it?  Is this Cox penalizing me for not paying for an overpriced cable box?  Is there some technical hurdle yet to be overcome?  Am I just doing something incorrectly?