@scotru I've taken a deep look at the issue and I can confirm there is no way to start the video using the available commands.
For a standard video player, it should be enough to say "select video" and then "play", or just "click video" to start the video. You can test these command in youtube.
Videos in Livestream are behind an overlay with a play "button" inside. When clicking the overlay or the "button", the video player it's initialized and start playing. This shouldn't be an issue for the extension since the "click" command would be the right command to simulate the click and then and start seeing the video. The main issue is that the overlay and the "button" are not clickable elements despite they look like that. Here the code that represents them.
Since Livestream video player doesn't follow the accessibility standards the extension is not able to play with it in a regular way.
This is not the end
I see two alternative solutions
1. Bother Livestream people to improve the video player and follow the web development good practices.
2. Implement a custom command for livestream. Handsfree for web can load custom commands, implemented by regular user, and extend the current voice commands suites. See https://www.handsfreeforweb.com/en/docs/
I'm not aware of your technical background, but I'd be happy to help you if you go for solution nº 2
Thanks for posting the issue