Long time since I've had anything go wrong with this plugin, so long time since my last comment. But alas, looks like the streak ended.
I just noticed that none of the fanfics I've downloaded from Fimfiction since around July 1st or so have cover images. A few test downloads suggested that FFF is failing to fetch valid cover images, so I tried debugging a bit by scattering prints() about to see where it's going wrong. As far as I can see the adapter itself is working correctly - it finds the right URL and passes it to setCoverImage, getting back a return value that looks correct. Following execution down into addImgUrl in story.py shows it getting into the "# explicit cover, make the first image." block. At this point I'm well into code that I haven't poked around in before and I won't have much free time this evening to learn it, so I figured posting here was a good next step. I've randomly selected
https://www.fimfiction.net/story/501587/ as a test example (it's recent and small) but the problem seems to apply to any story with a cover image. Given where I manage to get to in the code I don't think I've missed any obscure configuration settings anywhere, and this was working before with my existing config anyway so I doubt that's the problem.
Fortunately a test download of a story with inline images showed that FFF is getting those okay, so once I get this fixed it shouldn't be a big issue updating the stories I downloaded since whatever went wrong went wrong.