Experiment does not show up

I am trying to do an A/B test on our pages in Target Standard (not AEM). Creating a new activity, add two experiments (A and B) and finishing the process properly, activating it at the end. The experiments do not show up neither in preview nor on the page if I open it on CDN / origin (dispatcher) - I am getting an error in the browser console:

Uncaught ReferenceError: _AT is not defined

If the activity is configured for the publisher directly, it works fine both in preview and on the page opened.

So it seems that something might be blocked by the dispatcher. (One more note: targeting works properly if it is done from AEM 6.1 SP2 CFP4)

Do you have any idea? Please help.

Best regards, Gyorgy