I have CO 20.0 and decided to give it a try with the latest version from amazon and noticed on the last page it wanted you to install with a specific older version. shortly after the app crashed during install. I then tried the steps from the app page and they had issues with connecting to the internet.
I went to the wine page for the latest version and it had a tip to fix the issues.
select the latest installer and let it create a new bottle. when the popup for installing a font shows up go to CO and open the C drive of the kindle bottle.
Create all necessary folders to have the path "c:\users/crossover/AppData/Local/Amazon/Kindle/crashdump"
once the folder is created then accept the install of the font and let the install complete.
once completed the app will popup and bring up a registration window automatically.