Iframe autoplay not working in Chrome

This has nothing to do with Kentico and you can easily google "Vimeo autoplay chrome" and find the answer right away. https://help.vimeo.com/hc/en-us/articles/115004485728-Autoplaying-and-looping-embedded-videos

Autoplay Restrictions

If the autoplay parameter is present, our player will attempt to automatically begin playback. However, please note that some browsers specifically block autoplay. In these cases, your video will revert back to the original thumbnail and controls, requiring viewers to select play to start playback.

Autoplay is currently restricted in the following environments:

Chrome version 66+ (Desktop/Android)

Documentation: https://developers.google.com/web/updates/2017/09/autoplay-policy-changes Policy: Autoplaying videos must be muted. Videos that are frequently visited by the viewer are permitted to autoplay with sound (based on Googles scoring system)