Opening youtube on the site in full screen by clicking on the standard [+] button?

Question

YouTube

There is a site, on the main page the youtube container is built standard. I don’t understand what prevents it from opening to full screen when you click on the corresponding button in the player.
Thanks in advance for your reply.
Issue closed, thanks everyone.

Answer 1

Try to set position: relative and z-index: 9999
for the iframe. Parallax is obviously weird with its overlays.