Several of my apps won't accept keyboard entry in the iOS 10 simulator when compiled with XCode 8.
I CAN enter text by popping the visible keyboard and clicking on the letters. But typing using the keyboard doesn't do anything.
This is a known issue mentioned in the release notes and impacts some developers the very first time they launch Simulator.app:
The simulator’s hardware keyboard might appear disconnected on first launch.
Workaround: Select the “Connect Hardware Keyboard” menu item from the Hardware > Keyboard menu two times.