Problems with YouTube and oembed

Hello, does anyone know why the youtube oembed is no longer working?

I tried simply adding this URL in the post content: https://www.youtube.com/watch?v=HI3ErDjr4BY

or also using this code

echo wp_oembed_get( 'https://www.youtube.com/watch?v=HI3ErDjr4BY' )

and it returns false.

The same is on twentywelve