Not able to join some challenges

[Janus]

I must say I laughed at this. I couldn't join any of the duos listed (3):
https://www.youtube.com/watch?v=Nevg8Ic4_QE



   

So it's half an hour later and 2 of the challenges are still there. I still can't join them. Can anyone else join them? Just asking because they're easy ones, figured they'd have been done by now.

http://gyazo.com/bb84d41c69b366b599fd1aefcd673f8d