Animated Gif as cover in the app store

Hi,

I detected an app which has an animated Gif as cover in the app store. I created also an animated gif with this tutorial:
https://helpx.adobe.com/de/photoshop/how-to/make-animated-gif.html

Directly after uploading still on the edit app's description page the Gif is still animated. But if I publish the new description the gif is still again. Has anyone any idea on that?