If you go to that actual video https://www.youtube.com/watch?v=TbDyiwurjwI
and then go to “Share” then “Embed” you’ll see the embed code is
<iframe width="560" height="315" src="https://www.youtube.com/embed/TbDyiwurjwI" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
So the iframe URL is https://www.youtube.com/embed/TbDyiwurjwI not http://youtube.com/embed/watch?v=TbDyiwurjwI
I don’t know where you got http://youtube.com/embed/watch?v=TbDyiwurjwI from, but you can’t just construct URLs and hope they work, the server has to support them.