modal window with youtube video is not seen in the mobile

Hello, I only included a youtube video in the modal window with iframes. From a PC you can see perfectly, even narrowing the page, but when I open the modal window from my cell phone, you see the video for a moment and then it disappears (only the closing X remains). How can I solve it? Thanks in advance to those who will reply.

P.S. I cannot publish the site because the owner does not want to put it online for now (for the moment it is in maintenance mode)