I don’t see any sign of YouTube autoplay support in the click-image-to-load-video mode of FVP (in the current version anyway, I have not used older versions).
I did my own little hack that seems to work:
Added the following to my template:
wp_enqueue_script( 'youtube', 'https://www.youtube.com/iframe_api', array() , '1', true );
Added this to featured-video-plus/js/frontend.js, at the end of the jQuery.post() handler (line 85 approximately):
if (/youtube\.com|youtu\.be/i.test(data.html)) {
var id = $('#DOMWindow iframe').attr('id');
new YT.Player(id, {events: {onReady: function(event){
event.target.playVideo();
}}})
}
This snippet checks to see if the video HTML mentions a YouTube domain, and if so uses the YouTube IFrame API to play the video. Seems to work on desktop but i suspect it may not work on mobile, since you usually have to trigger play from a user-generated UI event (click/tap) to autoplay, but that’s a limitation that’s hard to avoid with FVP’s ajax content loading technique. Will do some testing and see. Hopefully this gets fixed in a future version and I can remove my hack.