How is your Url property defined? Does it have any attribute decorated? 

Hi!

No attributes, only standard declaration:

[CultureSpecific]
[Display(
    Name = "Url if user has free products",
    GroupName = SiteTabs.FreeCampaign,
    Order = 20)]
public virtual Url HasProductUrl { get; set; }

Do you have controller to your promotion/campaign? i.e. can visitors visit a campaign/promotion page? If not, I think that is the problem. 

Ok, but the code has not changed except for the upgrade and before I could drag-n-drop a promotion.
What you are saying is that the EPiserver.Url property is so smart that you cannot drag-n-drop items that not have a controller? Sounds a bit to complicated for me?

I'm not 100% sure but it sounds like you could do that before as a defect/overlook, and that is now fixed.

Why would you want to store the Url? Can a ContentReference be used instead? 

And the requirement is "Route-able", i.e. there is an Url that you can access the content. The simplest way to do that is to have a controller that can handle the content (i.e. a "template"). It does not specifically check for controller, btw. 

Sure, there are many possible way to handle it but it has worked before and you get a little confused when the function is not there anymore.

Thanks for your help!