xbee pro s2 action required

please help ! i have 4 xbee pro S2 in first time 2 of them when i connect them in xctu he said action required and press reset but when i press nothing happen before when i press he work ! and when i update the firmware the accept it in 115200 baud but after that they not work ! after 4 day the other 2 of them they have the same problem i dont thing that they are broken or no ! and what i should doing