Topics with PDFs attached have stopped working in SharePoint (RH 2019, new UI)

What is the form of the output when you view locally? If it's the same as what's produced for SharePoint, then it should have the same issue - if it's not, then your local test is misleading.

Yes, thank you, Jeff. Turns out there actually isn't a topic. Instead of a topic with a link in it, I think the way I set up these pages is that each one is like a link with no topic. And the link is the title in the TOC.

My current setup gives me the behavior I want, when viewing the help site locally (not on SharePoint). I want the end user to simply click the title in the TOC which opens the PDF directly. That's fewer clicks than opening a page and having to click a link on that page.

Any idea how to make that work in SharePoint?

I would have expected the topic page to be rendered in a .aspx format if going to SharePoint, but the link inside the page should be to the .pdf itself.

PPPS:  One last clue for you. I created each of these problematic topics via the "New page" button.

Is that the problem?

These pages do behave strangely in the authoring pane: if I double-click one of them, no topic opens in the authoring pane, just a blank area. It looks like this:

PS:  Setting up the topics as I have works just fine when viewing my help site locally. It's only when serving it on SharePoint that those topics throw the error.

PPS:  It's possible that this behavior (the error) has always existed and I just never saw it before b/c it works just fine when viewed locally.

Thanks for the troubleshooting, Amber. You've led me to the source of the problem. 

I had our SharePoint admin look at it. She shared this:

"The URL to the pdf is incorrect which is why it returns an error. The URL ends with an extension of "aspx" rather than 'pdf'. This URL would have to end in 'pdf' for the PDF to be displayed. If you simply replace the 'aspx' at the end with 'pdf' it works. Does RoboHelp generate this URL for you? If so, the issue would be with RoboHelp not generating the correct URL. "

So I'm thinking the problem is the way I've configured these topics. Whatever I've done is causing RoboHelp to generate the .aspx file extension instead of .pdf .   I've set them all up the same way, like this one:

Can you tell me how to do it properly?

Thank you!

Maybe check your sharepoint administrator hasn't changed any permissions or file settings?

Did you rename anything recently? Perhaps check that the location and name of the pdfs in Sharepoint match what the toc is pointing to? I'd compare both your local output and the sharepoint outpoint, just in case something isn't publishing correctly as well.