nav 2017 item pictures thumbnails not showing

Hi,
I try to demonstrate the new brick list feature with pictures (item in CRONUS). Unfortunately it doesn't work. NO picture in IE, firefox, Edge, Win client, Tablet app). Where is the problem? It shows "white" pictures in records having picture and and the standard greyed pircture for those without pictures.
The card page show the image correctly.
thanx for quick help.