Contents in left pane is empty after generating Webhelp

[lsb1098]

When I last generated  my Webhelp using RH 2019 Classic, my contents pane had the table of contents. But now when I generate, the content pane on the left side of the page is empty, even though I can still see the TOC in RH itself. I also still see the .hhc file in my src directory. This is what I see online:

Any ideas why it would disappear? I did not knowingly change my TOC or generation properties.

Thanks in advance!

[lsb1098]

So I played around with it and made a bogus change to my TOC, then regenerated. Then my contents showed up in the left pane. I then removed the bogus change and regenerated and it seems to be working now. Still curious as to why it would disappear in the first place and only reappear after I made a change to the TOC.