I gather you have missed all the posts about issues with Amazon changing how their ebooks are delivered on 2023-Jan-03.
For more information, check the Amazon forum, see
Amazon and DRM changes, in the calibre forum, check the stickied
Dealing with Kindle for PC/Mac 1.19 and KFX in calibre.
You will also notice that if you have an Amazon eInk device, that you can no longer Download and transfer via USB for Kindle Unlimited or Prime Reading borrows.