I searched the thread and found some old threads about this but nothing recent. My DD13 has my old iPhone 6 Plus 128 GB AT&T. A few weeks ago, it started going into "searching" mode unable to find a carrier. It was on 9.3.3. I updated her to 9.3.4, still had the problem. Took the SIM card out and tried it in my iPhone 6s Plus 128 GB AT&T it worked. I put my SIM in her iPhone, it did not work. Bad SIM ruled out. After a fruitless call to AT&T where they suggested that I purchase a new iPhone for her on the NEXT plan for only $xx per month, I wiped the device and did a full restore setting it us as a new iPhone. Still searching. As a "Hail Mary!" I updated it to 10.3 and it worked! Until last night. Now it's searching again. I went though a full restore to 9.3.4 and then to 10.4 and got it working. This morning? It's searching again. Looking on the AT&T forums, I have seen a few people mentioning this. On Twitter, I found that several more people are talking about it. Some of them are Sprint, not AT&T. This seems like an Apple issue. This iPhone is, and has been in an Otterbox Defender for over a year. Any ideas? Suggestions?