gamecenter on 3Gnetwork don't work

Question

I have a problem about the gamecenter,I am developing a multiply-player game, I have finished the connecting part, good luck, I can connect the another device to play the game over the local wifi, but I tried to do it through the 3G network and external wifi, it didn't work, it appeared that the interface stopped at the view of connecting the counterpart, that means they found each other, but they didn't found the match(maybe).Sometimes, one found the match,another one still stop at the view of connecting, it didn't enter the game, I read the log information, that told me the expected number of players was one, that mean there was only one player entered the game,another one did not, the max number was two.I found many website, but no answer, maybe is that because of the sandbox? I have tried in ios5 vs ios5,ios5 vs ios6 ,ios6 vs ios6,