I find that bewildering. How does one sign in to YouTube? I've never done it. And if you click on a YouTube video that's embedded here and are asked to sign in, clicking on that doesn't have any result. You must, as I think I said, refresh the post and then click on Watch at YouTube.
I tried to copy the window, but copy and paste works differently with the different Mac OS I have now. It's very easy if I can drag and drop, but becomes complicated if I try to do it any other way. And I'm just too frustrated to keep on trying.
So let's see if this works.
It says, "Sign in to confirm you're not a bot. This helps protect our community." Then there's a clickable "Learn more". If I click it, the whole box goes away. It comes back if I refresh the page. There is the option to watch on YouTube once you've refreshed.