After seeing many posts, I decided to look into it further.
You can NOT use the paste URL option.
I went back as far as, 6267.
Can only guess something changed as far as this via YouTube.
So, for now, copy and paste the URL into SF address bar.
Putting YouTube links in the address bar works, or just navigate in SF to YouTube and click on videos you want downloaded.
You can rant and complain here in the community or contact SF feedback (https://www.dvdfab.cn/contact.htm)
Disclaimer for current, longtime and new members, we are all only long time SF users with added knowledge of fixing some issues and reading logs. NO one here that I know of gets paid to help. The only official SF employee here (who does gets paid) is Wilson Wang, AKA, StreamFab, MusicFab Product Manager