The Video Block is used to insert a video. You can either upload a video or paste in the link to a video elsewhere. YouTube, Vimeo and other online services do not work in a Video Block you should use the shortcode block.
⚠️ Using the Upload button may not embed the video if you publish quickly. It is best to click Media Library and upload the video there.
There are a lot of setting that can be accessed from the Block Settings sidebar. This can be accessed from the Block Toolbar or the general setting menu.
Onice you have opend the sidebar you can add a Poster Frame, an image to show before the movie plays, turn on looping and auto-play.