I have the same problem,
Do you know if your feed utilizes Vimeo, at all? We've had some other reports of Vimeo feeds with channel issues.
Partner Success Manager
I just checked multiple channel feeds that use Vimeo and they are all reporting that the video URL is unreachable.
I also double checked the individual video URL's in a browser and they where all loading fine.
Thanks @AaronMSpelling, I was posting here as it was the top thread at the time. I'm aware of the other thread.