I have ZenFone 2. When I traveled to Taiwan, I used the sim card from TaiwanStar, it worked fine. But when I returned to USA, I replaced it by the original sim card, and it cannot be detected. I have experimented by swapping the sim cards in two slots, and trying one sim card in only one slot, ect. And it works now. My impression is something is sticky inside that I do not understand. But if you swap the sim card a few of times, it should work.