SharePoint / OneDrive image in adaptive card doesn't show in Desktop Teams
When adaptive card is send to Teams chat image in this card which is from SP or OneDrive is "undefined". It happens in desktop app. But when I look at this adaptive card message in web Teams app image is displayed correctly.
For some reason Teams desktop app doesn't have permissions to view the image.
This issue is described also in link below.
Add the thumbnail property of the file to the adaptive card instead of the direct file URL.
The thumbnail property contains an access token and the URL to the thumbnail, so in theory you could use the thumbnail anywhere.
Maciej Musialik commented
I have exactly the same issue. It's actually stopping me from using flow and adaptive cards for few of my use cases.