No thumbnail for news links

Hi,

I noticed that thumbnails of links are not showing here https://lemmy.world/c/world, whereas same news link posted on https://lemmy.ml/c/worldnews is working fine, why is that?

Here is an example of the same news link on both communities:

https://lemmy.world/post/260407 (no thumbnail)

https://lemmy.ml/post/1317159 (with thumbnail)

Thanks