If you are uploading Jetpack videos on WordPress 5 you are going to need to go through some specific steps to get that to work. The built-in Video Block of WordPress 5 will not work.
If you have not upgraded to WordPress 5 yet, don’t. Wait for WordPress 5.1. WordPress 5.0, 5.0.1, and 5.0.2 still have a myriad of high-importance bugs like disabling CSV imports and exports for many plugins.
Getting Jetpack’s Videopress hosting to work on WP 5
Despite what Automattic’s support team might tell you, and you’ll get different answers depending on who replies, do NOT use the Video block in WordPress 5. To upload your videos insert a Classic Block and use the media button to upload and insert your video.
This method should upload the video to your server, then trigger Jetpack to copy it over to the Videopress servers and return a standard Videopress shortcode. You can use the Edit As HTML option on the top-right menu of the Classic Block to view the HTML and check for a Videopress shortcode.
It should look something like this:
That’s all there is to it.
Jetpack Support is confused
You’ll hear different stories depending who replies to your Jetpack support request. The first person wrote back…
You can use the Classic block to embed CDN-hosted videos but you don’t have to. We also have the standard Video block which should obey the site settings (ie: use the CDN if enabled) as well as the VideoPress block which should always display from the CDN-hosted URL.
Later in the very same email thread a different rep picked up the request and wrote exactly the opposite.
You expect that you can upload videos to our Jetpack Video Hosting by using the Classic block?
At the moment, our Jetpack Video Hosting feature has not supported uploading videos in the new block editor. That is, when using the Classic block and uploading videos, you’re uploading to your own hosting, not our Video Hosting.
For my site, Classic Block add media worked. Nothing else did — though the Video Block has a nice interface that inserts the local (as in on your laptop’s hard drive) video which will “upload” and play immediately but does NOTHING on the back end. As soon as you close the editor or post preview page the content goes away. Makes sense as a file:// URL will only work on YOUR laptop and only while the browser session is active.