I have used Calibre and associated plugins on my kindle books for years with no issues. I have Kindle for PC set not to update, and am using version 1.31 as always. I'm on Windows 10, Calibre version 6.4 and the latest plug-ins.
I've had a large number of Kindle books in Calibre for several years, already converted to epubs. Suddenly, the titles are still there but none of them have ANY associated book files with them. No kfx, no epub, no azw. Nothing.
When I tried to import them from my Kindle library on the PC again, I couldn't find them b/c Kindle doesn't use names, only their numbering system. So I renamed that folder to My Kindle Content old, and started a new one. I removed the books in the Kindle for PC library, and started to re-download them. I tried several older books first, which i knew I had acquired several years ago before DRM changed, etc. Examples Uncle Tom's Cabin purchased in 2011 and Adventurous Boy's Handbook purchased in 2011. when I redownload them to Kindle for PC, then try to import them into Calibre, they come in with a title of whatever letters and numbers Kindle is using to identify, and they cannot be opened.
So, I noticed that when I click on the title of either book from the Content page of my Amazon account, it goes to a 404 page, like they no longer carry the book. So maybe that's why it's acting up.
Next, I redownloaded a book I just bought in Aug 2022 The Cabin in the Woods. It also comes into Calibre the same way, unreadable title and a warning that it cannot be converted because it's kfx.
I have followed all the instructions from the post explaining how to deal with kfx and don't know what I am missing. I can post the error file if that would be helpful but it's long.
If there is no way to convert the newer books I understand and can read them on my tablet with the kindle app, though I prefer the e-ink reader. (Kobo Libra)
But I don't understand how all those book files were lost in Calibre. I have never knowingly moved any files and it seems weird that the only missing ones are originally kindle books. None of the epubs I've gotten from Google books, B&N or Kobo have been affected.
Any help appreciated.
update - after writing this out I read through all of the error message and found the link to harper's FAQ. Rereading that again I realized I need to revert to version 1.19 of Kindle for pc so am doing that now. I know I had that version at one time and have always set it to not update but somewhere it did. <facepalm>
Still don't understand how Calibre lost all those azw files though.