multiplayer problems on minecraft PE V0.12.1 alpha

I have 3 Ipad, 2 Iphone, After this upgrade recently, non of them can join each other as multiplayer mode. we have the multiplayer button on. we all connected on the same router. but other people's world never pop out again after this V12.1 upgrade.
we played this game for ages. my son and daughter are very sad these days.