We can not fetch videos from this type of page.
Your URL was: http://www.youtube.com/verify_age%3fnext_url=http%253A/www.youtube.com/watch%253Fv%253DFfVjzOBV7wA
The URL must be like http://www.youtube.com/watch?v=KPtX7hak0Qs
https://www.
and replace with pwn
Example: