When I try to publish to SharePoint, Robohelp downloads a text file and "about:blank shows up in Chrome.
I am using 2022.2.22
Is it working if you generate output locally?
Yes it does.
Ok, so what happens if you transfer that aspx output to the SP site? (outside of RH)
It's very strange because when I upload a project to SharePoint for the first time it works fine, but if I republish it again it's starts downloading .apex files to my local drive and it opens a tab in Chrome with nothing on it.
That sounds like something isn't configured right on the SP site - others have reported something similar when they go to look at a topic, it tries to download it instead of display it in the browser.
See if this thread helps. https://community.adobe.com/t5/robohelp-discussions/robohelp-2020-error-in-frameless-deploy-of-the-p...
My site www.grainge.org includes many free Authoring and RoboHelp resources that may be of help.