Thanks for trying to help me out. I started using Calibre in January 2023. At that time I successfully imported all my existing Kindle books (bought from Amazon) into Calibre without DRM. I later installed the Annotations plug-in, but found that it only imports annotations from the books I downloaded to my Kindle before March 2021. All the books (both before and after that date) are on my Kindle, and I can open them just fine and view the annotations on my Kindle. I also tried it on an older model Kindle (Keyboard) as well and got the same result. For some reason when the plug-in enumerates the books on my devices, it’s not seeing the ones downloaded from Amazon after ~March 2021. I’ve poked around in my device file system and cannot find any obvious difference between the books it does find and the ones it doesn’t. It may be an internal file format change.
I just tried installing a book onto my device directly from Calibre (per your recommendation), and the Annotations plug-in *does* in this case find the book and import the annotations correctly. So it appears to me that there is something about the way that Amazon saves books on the device that changed around March 2021 that breaks the way the plug-in enumerates books on the device. I did note that the directory structure that Calibre uses to save books on the Kindle is different than the way Amazon does.
As I read on multiple devices, I’d like to keep downloading books via Amazon (including side-loaded content) as it makes it easy for me to access the same content on all my devices, as well as track where I am in the book. I also just discovered that it’s pretty straightforward to access my Kindle annotations via
https://read.amazon.com/notebook and select all/copy/paste them into my Annotation column in Calibre. So I’ll use this as my workaround going forwards.
Thanks again for the help!