after updating IOS 9.3 on iphone 6S, the phone turned itself off in the middle of the night and will not turn on. I tried hard reboot and also tried connecting it to my computer and using iTunes. nothing is working. I had issues with the original 9.3 IOS update on March 25th and had to install the update using a hard connection with iTunes. The update appeared to work, but during the night of March 27th , the iphone, while plugged in to charge (about 70% battery life remaining when I plugged it in) seems to have shut down and will not turn on,
any suggestions would be greatly appreciated.