Plain text html in posts works, but merchant banners don't display at all

I am working on an affiliate marketing site called “EtherMall” and am using TheShop” as my theme/template. I am trying to create two extra posts of merchant products based on their sale/coupon banners and their hot sellers banners. I can get the plain text ad/links to work fine. But for some reason, when I try to add banners, nothing s displayed at all (I also observed this same problem when I was trying to use pages instead of posts).

When I add full pages of code from ShareASale’s Make A Page, it all displays perfectly.

I have tried just the banner code, the banner code wrapped in CSS (as shown in https://www.siteground.com/tutorials/wordpress/banners.html):

<div style="display: block; margin 10px auto; width 480px">banner code</div>

I even, just to rule out the possibility that, for some strange reason, text might have to precede or follow banners, adding plain text above and below both of the above attempts. Obviously, that didn’t make any difference—the plain text was displayed with an empty space in-between.

As I mentioned, plain text (html) merchant ads display fine. It seems that it’s only when a linked image (visible when I link to it directly) is added that it always fails.

What (no doubt obvious to anyone but me) detail am I missing here?

Thanks,
Jim Graham ([email protected])