playlist does not play

Hello. I’ve added to the playlist page with this code https://www.youtube.com/watch?v=8Vu5AE8OyQ4&list=PLRDR_sr_1eaT4uiRPhj406W5FXKWRUIZt&index=1&layout=gallery. But the video except the main one at the top of the playlist cannot be played back. They look just like the picture. Here is the website http://vestnikyar.ru/page/video-gallery/

https://ww.wp.xz.cn/plugins/youtube-embed-plus/