Hi, my understanding is that some browsers block auto-play, apparently the only way to change this is for the viewer to change their browser settings.
I used this for SL import, I added a blank slide in front of the content slide with a "Jump to Next slide trigger". Next slide being the video. It plays automatically in Rise. (tested in Chrome)
Downside is video starts playing automatically on page open and does not stop until it ends. So if it is a scroll page, with content before it or after it, you hear the video before you reach it and, after you scroll past it if it hasn't ended.
OR, I did find this it's a tad more involved, not sure what format it is, you may need to make SL into another format. I haven't tried it out, it has how-to directions... https://anthonyvecchi.com/RiseVideo/index.html#/
