It wasn't working the other night for me either. My hypothesis is they have it on a timer so you can't look at Disneyland while it's shut down and they are working on the park. Could just be down for a bit, though.
Around 3 PM yesterday, I went to the Mattercam and all I saw was a light bluish color. I thought it was my laptop but turns out it was not. And like Radiobarry said, I get an error when trying to go to it.