Here is the screenshot. My main notebook is just called "Inbox" but the space where it would show up, with 1k+ notes, just doesn't register. Whenever I try to access it manually, or categorize a note into that notebook, I see this kind of screen. When I try to categorize a note into that notebook, the screen just flutters and ticks. It seems like the program knows the notebook is somehow there, but can't interact with it. Strange.
I submitted a ticket! Thanks.