Unfurlink Link (Adaptive card) in

Kzawadka I found the following solution: apparently the attachment requires a preview defined when returning an Adaptive Card.

Here a snipped how it works in Javascript:

 const adaptiveCard = CardFactory.adaptiveCard(card);
 const heroCard = CardFactory.heroCard("card title", "card text");

 const attachment = {
   contentType: adaptiveCard.contentType,
   content: adaptiveCard.content,
   preview: heroCard
 }