I don't know if this is true on hubpages, but I had to call Amazon last week for my business website (actually was able to get a person). If a website is secure with an https, amazon ads will not appear. I took off the ssl license on my website that didn't have a merchant account, since ssl is important for website where your customers give credit card numbers, but not important on other websites where credit cards are not involved. The way to tell if a site has an http is to go to Internet Explorer and put in the www (address). You'll see what comes up - an http or an https. I just put this address in and it's an http. So all of that above might be irrelevant.
2nd thought - All Amazon ads are not created equal! Simple product ads show up easily on my website. If it's a widget - not so much. You'll also notice at Amazon that some ads run on mobile devices and others don't.
Actually, just before I got distracted here on hubpages a few minutes ago, I was just about to grab a google ad for my business website after deleting the Amazon ads altogether. It's simply not worth it. I do my website building with godaddy and even the rep there, when explaining my ssl answer from Amazon said, "Why doesn't Amazon simply make the ads work with either http or https?" My thoughts exactly.
You CAN call them. They're very nice. You have to hunt around a bit to get the number, but you can call for ad help. I'll be interested to see what others say or what you find out because, quite honestly, I'm done with Amazon widgets, banners, etc. and am only going to do product ads if I do any at all. Hear that Amazon?