Suddenly today, one of the site books URL could not be found. The only thing different was that I updated a 3rd party plugin - SVG Support - Version 2.3.4 | By Benbodhi
Do I even need an SVG plugin or does WP continue not to support this format?
The site had been working fine up to now. All other sites on Pressbooks network are working fine. I deactivated the plugin but no change in URL not found. Dashboard and visit display URL not found. Very strange.
Operating with the WP 4.7.1, PB 3.9.6 and PBT 3.0.1
I was able to bring back the site by changing the site url to i.e. /epub1/ and everything works. I believe now that the issue is related to a file named epub in the root directory placed there by a system admin. Will need further research to validate hypothesis.
Further research has revealed that an image file with the filename epub.on.pi was blocking the site named …/epub
Solved!.