Hello Alexis Chams,
Thank you for reaching out to Microsoft Q&A.
Since your PC is still running Windows 10 and cannot be upgraded to Windows 11, the issue appears to be related to the current Kindle application's system requirements rather than a Windows setting.
Amazon states that the legacy Kindle for PC application is no longer supported as of June 30, 2026. Amazon's current desktop Kindle requirements list Windows 11, and for an unsupported operating system Amazon recommends using Kindle for Web.
Unfortunately, if the current Kindle application does not support your version of Windows, there isn't a Windows setting that can make the application compatible. Since Windows 11 is not an option for this PC, I would recommend contacting Amazon Kindle Support to check whether they provide another supported method for offline reading on Windows 10.
I hope this helps clarify the situation.