Thank you for leaving this message. Please ensure you are using Chrome browser to download Kindle cloud reader books, not safari.
Also, please install kindle cloud reader app to your chrome: https://www.epubor.com/faq.html#e901
Then run log in your amazon cloud reader via chrome browser and download the kindle books. It should be working this time.
If you are still failed, please contact our technical support: support@epubor.com to get further assistance.
on my Mac.