Sorry. Nothing "just happens".
I know. That's why I'm confused. You'll have to trust me on this.
But, guess what! It just as mysteriously has started working! The article in question is
here. I just went back to it to confirm and I noticed at the top:
[FBDISCUSSBOT DEBUG:Searching for {mos_fb_discuss:#} tag in article text... Found one! ][FBDISCUSSBOT DEBUG:Found the FB threadId in the cross reference table(#__fb_discussbot). ][FBDISCUSSBOT DEBUG:Counted 1 posts in this thread. ][FBDISCUSSBOT DEBUG:Showing First posts in the thread in Ascending order. ]
????