Video background on Facebook

I recently created this web page and it turns out that when I post the link on facebook the background video does not appear, not even an image of the video frame. (see attached image). I tried putting a picture of the frame under the video, but it doesn’t seem to work. How can I make a picture appear when it is not possible to play the video?
Thanks for your help…

Here is my site Read-Only: Webflow - Fabriblocos