Wonder Challenge impossible to start

So I decided to check out the new Wonder Challenge mode added recently. Everything went fine and dandy until I picked out a Delta Charmander... and then the game got stuck at the "Preparing to Wonder Trade..." message. No matter how many times I pressed Enter, the game always repeated that message.

I know it's a new challenge mode, so there are still some kinks to be ironed out. But not being able to even do a challenge is a bit annoying, to say the least.