This is a bit off topic, but since it came up here, I'll post it here...
Can’t see the video without logging in to prove I’m not a bot…
I've suddenly been getting that on pretty much every embedded YouTube video the past week or so. To say that it is extremely annoying is an understatement -- especially since I get it even when I
am logged in!
So I did some playing around with different browsers and settings and such, and at least for right now, I have it working again. I'm on a Mac using Safari, but I've tested other browsers and they all seem to be the same, so this fix should still apply. I have Apple's "private relay" on, as well as a VPN (I had the VPN before private relay existed). The only way Youtube would work was to turn off
both of those. But... I played with the VPN settings, and the VPN protocol had been set to "automatic". I changed it to "OpenVPN (TCP)". and now YouTube works again, even if I'm signed out, and even with both the VPN and private relay turned on.
I realize that won't apply to everyone, but I hope it helps a bit.