Direct answer
When URL fetching fails, first confirm the page is a readable public HTML chapter page. If it is not, or if the source begins blocking or rate-limiting the requests, stop and use Manual Entry for the affected chapters.
Common causes
- The source requires a private login or heavy app shell.
- The response is not standard readable HTML.
- The site rate-limits or blocks the sequence.
- The page is a different document than the story chapter you expected.
Clean fallback
The reliable fallback is Manual Entry. Copy the chapter text from your browser, save it as a custom chapter, and continue building the binder without trying to outsmart the source site.