Is co op working for anyone else?

I bought the Shrek DLC and I've played through about half of it, and one of my friends bought it to play through the other half with me. Whenever they try to connect, it will buffer for a minute or so and then say that they can't connect to host.

We've tried switching to a different network (both networks are stable), restarting the game, restarting our computers, but nothing is working.