NewsFeed in classic view not showing video thumbnails

I am trying to post a video in Newsfeed . No matter what i do , from streams or youtube, video thumbnails does not show up. According to this post https://support.microsoft.com/en-gb/office/add-features-to-a-newsfeed-post-155f0b0b-5438-4a91-80fa-d56ffb22b4cd?ui=en-us&rs=en-gb&ad=gb

it should work. But i cant get thumbnail or display as working. It just shows up as a link.