Video link 'blocked' on Constant Contacts

Hi, I've been trying to add a video link to my landing page/email and the Youtube link keeps coming up as 'blocked' when clicked.

I've tried linking a picture as I know the embedded video feature is just another link, and I've tested both with public and unlisted videos but they're still blocked. I've also tried as just a link via button but nothing either.

Is this because it's a Youtube link? I'd use Vimeo but the video is too big and our office won't need to use Vimeo so no point getting an upgrade for it to work.