ffmpeg? See nothing under test

Is FFMPEG installed on your server? You can make thumbnails without it. FFMPEG just helps with encoding videos into other formats and automating thumbnail creation.

I don’t know how to find it out

If you don’t know how to find out, then you almost certainly don’t have FFMPEG. It’s not allowed on most servers unless you administer it yourself.

No it is shared space server ??

You wrote:

If your video can be played natively in your browser, or if you have FFMPEG installed on your server

Is there any other possibility besides ffmpeg, which I don’t have on server, to create thumbnails from embedded videos?

You can make thumbnails of most videos in your Media Library without FFMPEG. https://www.wordpressvideopack.com/docs/add-a-video-to-a-post/

Thank you but videos are not in media libraray. I meant embedded code from other sites…

Oh, I don’t know any way to do that.

??

thx so far!