It’s because you’re on the Full view and haven’t selected a story. I turned on the auto-select a story preference and it should now work as you’d expect.
The bug here is that if you scroll down you’ll see a “Select a story” notice, but for some reason it’s super low.
Oh wow, I didn’t even see/consider that bottom set of buttons that lets you pick viewing one story at a time. I don’t know how I would select a story in that view because the only way to select a story that I know of is within that pane, which is now showing nothing. At the very least, maybe that text could say “you’re in story view and haven’t selected a story; select a story or switch to feed view” with a highlight, arrow, or screenshot of the bottom left of that pane. I must admit, I never look or see that bottom bar. I might as well not exist.
Any chance that other linked bug could get some love?