I can't solve this despite my best efforts. I also consulted the Apple documentation and several related questions here and still I have a mental block on this.
Using Xcode 6, I embedded a table view controller in a navigation controller and could set the title of the navigation bar in the table view controller, but not in the two view controllers that are connected to the table view via segues.
I did think there was a navigation bar on these two view controllers because after I embedded the table view controller in the navigation controller, it blocked out my topmost textfield in both. I repositioned that so that isn't a problem, but in storyboard I still don't seem to be able to click inside the navigation bar to add a title and now having added a navigation bar manually to test it out, I can see that there is only one navigation bar in document outline.
So do you simply have to set the title of the navigation bar programmatically or with an IBOutlet or some such? Doesn't seem like you can click into it in story board.
I am pretty sure this is a bug in Xcode... I have experienced the same issue and most of the time it was solved by restarting Xcode.
** In addition you may be able to get it solved by doing:
Drag a Navigation item from the objects pane into the viewcontroller or tableviewcontroller. This seemed to work for me. I did notice that the navigation area was missing from the "Document Outline Pane".
I hope this helps.