OK - I have found it - because of some reason I had to change View Tint color to other than default and now nav buttons are visible

Thanks for respond. My setup is as you said. I have found out that when I recreate Main.storyboard then it is working or when I create new project from the scratch then it is working too - so most probably its some issue with my storyboard (legacy project) - but what can it be ? What is working is that when I click in the place where "back" button should be then Im redirected to prev page - which is fine - but somehow "back" button is not visible.