This problem is occurring on Intel and M1 processors. Simply uninstalling and reinstalling the app doesn’t work, so what should you do? There is a new workaround that will make Kindle for Mac function again.

In order to get the Kindle for Mac app working again, you need to uninstall it. Next, you have to visit Users > Home > Library > Application Support > Kindle folder and delete this folder and then visit Users > Home > Library > Containers > folder and delete this folder too. Once both of these folders are deleted, you can reinstall the Kindle for Mac app and it will work again. If you are running into the problem where Apple is refusing to even install the app, you might want to look at their security and privacy guide settings, it walks you through how to safely install apps that are not found on the Apple App Store. This tutorial primarily works if you had the Kindle app installed, before you upgraded from Catalina to Big Sur. If you still run into problems, you can always access the Kindle Cloud Reader in Safari.The Kindle for PC and Kindle for Mac programs use Amazon's KFX format for most books. Each book will appear in a separate subdirectory of the 'My Kindle Content' folder with a file extension of '.azw'. Unless additional steps are taken, these books will fail to convert in calibre with the error: 'KFXError: This is an Amazon KFX book. There are several methods for either avoiding or handling KFX format. Method 1 - Revert to an older version of Kindle for PC/Mac The following descriptions apply both to Kindle for PC and Kindle for Mac unless one is mentioned explicitly.

Launch Kindle and under the menu choice 'Tools', 'Options', 'General', uncheck 'Automatically install updates when they are available without asking me.', and save.(Note: This is a 32-bit program and so it is not compatible with MacOS Catalina and later.) Older Kindle for PC/Mac version 1.17 can sometimes be installed to work around this problem. (Note: This option is not available in some Kindle for Mac versions.) Delete the contents of the 'My Kindle Content' folder within your 'Documents' folder.Download and verify version 1.17 of Kindle for PC/Mac.Install the downloaded version 1.17 software.

Download kindle for pc version 1.17