is reporting {"error": "Not Found"}'

I was able to publish an Rmarkdown/shiny doc to a few weeks ago.
Now I cannot republish. A popup says:
"Your content could not be published because of a problem on the server. More information may be available on the server's home page If the error persists, contact the server's administrator. Error code: 404.

Following the link, the page only has the following:
'{"error": "Not Found"}

I have re-authorized via Tools/Global Options/Publishing. Didn't help.


It looks like there were files needed that the automatic manifest assembler was not able to detect. I added them using the Add feature in the Publish window. All is well now.
It helped to look at the log files through the page.