windowContent not displayed

M1Pro running macOS 12.5 & Xcode 13.4.1 developing a macOS application using storyboards

simple beginning to an app: appDelegate, a custom windowController, and a custom viewController windowContent set in IB using drag no error reported during build

when run: windowWillLoad is called viewController viewDidLoad is called window didLoad is called appDelegate applicationDidFinishLaunching is called window is drawn on screen but nothing appears in the window

view has 2 verticalStackViews, a tableView, and a horizontalStackView

I'm stumped....
Any thoughts appreciated on how to track this down!

windowContent not displayed
 
 
Q