I tried to compile a MOBI file after upgrading to Catalina and discovered KindleGen is not compatible. I checked the Amazon site and there is nothing related to the new OS - go figure. I (luckily) still have the old OS running on my laptop so was able to produce my Kindle file there. Any news on when and if Kindle Gen will be updated or an alternative to produce a clean Kindle book directly from Scrivener? BTW - the epub compile worked great, as usual.
Apparently there is a newer version of Kindlegen available as part of the Kindle Previewer. Might be worth trying that:
Found the app and downloaded it - thanks for the info. Problem - running under Catalina a message says it cannot be installed because Apple cannot check it for malware, and it needs to be upgraded. The beat goes on … thanks anyway. I’ll keep working on this. I’ll keep my laptop running the old systems for a while in any event. I do not care for the conversion processes - never been happy with the results.