Please find the link with the image included: https://3ec.live/bug/

Notice that there is a play button in the middle of the screen. The movie does not auto-play when the play button is present. Pressing on the play button does not play the movie.

I have a feeling that this may be an internet bandwidth problem, and the movie is not playing in low-bandwidth situations. However, if that is the case, the ‘Play’ button should not display since, well, it cannot play.

I do have extra CSS which you posted elsewhere in place, and it works under normal situations where the bandwidth is normal

#wp-custom-header-video-button {
    display: none;