iOS Keyboard (inside UIRemoteKeyboardWindow) is Not Shown When UITextField Becomes First Responder in Touch ID Completion Block (iOS 10)
As a temporary workaround, call becomeFirstResponder
after a delay fixed this, however, not happy with the hacky solution.
Looks like the issue occurring for different scenarios too - keyboard could be invisible even if you are selecting the textField manually after cancelling touchId alert.