Traffic has been drastically down for a lot of people, so there's the possibility it's that. With a few years of dealing with Ad Sense, I tend to think nobody is blocking anything so they won't have to pay. Have you double-checked your affiliate settings to make sure you haven't inadvertently left out your Ad Sense code (especially, maybe, since HP ads have involved some actions involving codes, etc.). I know I'm only one person, but I've always been very satisfied with the way things are done with the Ad Sense program. Payments have arrived on time and/or early each month. Technical glitches can happen, of course, but I do doubt it's something anyone has done intentionally. (Again, though, this is only one person's opinion/experience.)
By the way, if you HubPages ads enabled on your account people may be clicking on those instead of Ad Sense ads.