Well I’ve fixed this issue myself. AMP pages will not show ads with the normal ad code. So if you have any existing shortcode of function that you use to push ads within your content, put a check in there like this:
if ( is_amp_endpoint() ) {
.....
}
and then use the adsense ad code the way @crischo has mentioned above
I think it’s because you are trying to fetch out wide ad. Please note amp is only for mobile and wide ads no way make sense for mobile. Try using 300×250
I’m using the Custom AMP plugin in addition to the official one – it includes a lot of extras like featured images, related posts, and Adsense in the footer. All of it validates, per Google Webmaster Tools (I didn’t try adding a menu so not sure that would work).
Ads are supported; but not everybody serves ads in the same way.
So, you need to learn to use the working methods such as the filter added to your functions file to enable the kind of ads you serve; either adsense using example provided above, or shortcode to an ad rotator plugin, etc.