This started happening around two weeks ago. I use matched content with ads and it's blank sometimes, which makes no sense because it's not an ad. Normally it would show without the ads when there are no ads available, but now it's all blank. Why?
I went to HTTPS months ago and never had a problem with matched content ads not showing until about a week ago. Now half the pages don't have them, and by half the pages I mean about 20,000 pages. Just a huge white space where the matched content should be.
Adsense is in the process of evaluating each page with its Mediapartners-Google bot as part of the upcoming Initial Better Ads Standards [betterads.org] compliance and until each page is evaluated, ad space may not get filled.