Well that worked in an unexpected way!
For your own sanity have a look at the new canvas (opengl reachable via F11 or the view menu) It has some nice new features.
One "feature" was that it captured my cursor, so once I'd started the pour outline, I couldn't move the cursor out of the window in order to click "Okay" on the Copper Zone Properties dialog -- instead the cursor stayed in the pcb layout window and started autoscrolling. I had to switch to another app and back to free the cursor.
Did you press "B" to "refill" the zone?
Once I completed the outline in OpenGL mode, the fill showed up without typing B.
For completeness, I undid the fill and switched back to default view mode and repeated the process. This time it did not capture the cursor (as it had in OpenGL view mode), but DID require me to type B ("Fill or Refill All Zones"). And voila -- the fill appeared.
That solved my problem - thank you.
Post-facto analysis: The tutorial says "Right click inside the area you have just traced. Click on Fill or Refill All Zones." As far as I can reconstruct, I did right click, but somehow missed that menu item.