I have the same problem with an amazon affiliate iframe / use the code-block but nothing displayed
I found the problem, but I cant solve it!

The code is ( … marketplace=amazon&region … )

<iframe style="width:120px;height:240px;" marginwidth="0" marginheight="0" scrolling="no" frameborder="0" src="//ws-eu.amazon-adsystem.com/widgets/q?ServiceVersion=20070822&OneJS=1&Operation=GetAdHtml&MarketPlace=DE&source=ac&ref=tf_til&ad_type=product_link&tracking_id=memaad-21&marketplace=amazon&region=DE&placement=B010UFKDHY&asins=B010UFKDHY&linkId=&show_border=true&link_opens_in_new_window=true">
</iframe>

After hit “Save” nothing displayed. When I take a closer look to the code (again in code-box) there was an automatic change:

from marketplace=amazon&region -> to marketplace=amazon®ion