If you’re using Chrome and your version is between:
48.0.2564.82 and 48.0.2564.97
You will notice that external scripts that are loaded over http are not loading because they are blocked by Chrome. It appears that clicking the shield icon to "allow scripts" only allows scripts on the main page (not your iFramed website).
In the mean time you can work-around this issue by using a different browser...
It will be interesting to see how long it takes for them to fix this.
Correct... Although, it's actually the other way around. (script is HTTP while main page is HTTPS).
Anyway, that's not important. Normally, by clicking the Shield icon in Chrome on FF you can allow scripts/css with different protocols to load onto an HTTPS page (thus allowing Target to work with non-https websites). However, there was a bug introduced on 01/29/2016 that broke the "shield" functionality when a site is iFramed (which is the case with Target Premium).
Please read the linked issue on the chromium dev site for a more detailed explanation of the issue.
Also, I've verefied that this works fine on Firefox when allowing "unsafe" scripts.
If you are using the current version of Chrome and Target Premium, you should be able to re-create the issue if your site is served over HTTP.
I've attached an image of the Adobe Target notification that describes the "shield" icon.
"We are ratcheting down on mixed content, and are intentionally making it more difficult to execute mixed script. We intend to show the shield less often, with the eventual goal of removing user-visible surface entirely."
It will be interesting to see if Adobe drops Chrome as a supported browser for their "Enhanced Experience Composer".