What does full screen mode in embed youtube video depend on?

Question

YouTube

I noticed that in many youtube videos on third-party sites there is no full-screen mode:

(double-click on the video also does not work).
At the same time, the same video is normally embedded on other sites (for the test I tried to get the embed code and add it to my blog) and other videos on the same site where I found the first video work fine. I met such videos without fullscreen both on Facebook and on small sites.
What does it depend on? Any privacy settings, manual banning of domains in the account of the author of the video, or exceeding the number of video views in a specific place (from a specific domain or page)?

Answer 1

allowfullscreen parameter in iframe code helped.
iframe width="300" height="250" src="//www.youtube.com/embed/..." frameborder="0" allowfullscreen