Other people are getting in, I don't know how how. Can you explain?
Wait at least five minutes. Even though the spinning "www" may have vanished, he space may still be loading. So wait about five minutes and try again. It's worked for me when playing this game and the broomstick racing game.
If you wait a few minutes like conrad said you'll get to play the tutorial wizard duel and the time trial at the broom races but that's it for me anyway. When I try to play anything with another person I get an error message saying my connection isn't suitable for this activity or something along those lines. Last time I tried to play was Friday and it was like that for days before.