Hello, Team!
I just learned that Scrivener 3 beta for Windows still lists KindleGen as a way to save my book as a Mobi file.
However, Amazon no longer supports KindleGen.
So, I recommend that you either remove any references to “KindleGen” in this new version of Scrivener 3 for windows. Or, find a way to include “Kindle Previewer 3” as a functioning part in the compile process.
Thanks.
Amazon no longer provides KindleGen as a standalone download – but as you mention, if you install Kindle Previewer on your system, there is an updated version of KindleGen included. And lo! Scrivener v3 already knows to look for it and use it!
FYI, this is already on our internal list of needed documentation tweaks. – Katherine
You have to export to ePub. I do pre-flight testing in Sigil and then check it again in Kindle Previewer. Works fine.
A huge disaster. 
I tried to use Scrivener in Windows. I found many rpoblems. Tables reformat by magic. Sometimes the only way to continue with copy + paste from Word it’s to wait until the next day. And finally I was ready to compile. Dowload the Kindle previewer and… Nothing. Error and error. Scrivener does not recognize KP. So, I tried epub. Error again.
So, I have been working non stop for nothing. I am so mad that I have no words. Well, I am goig to my twitter account with my 4300 followers, writers mostly because I work in publishing (no, I don’t need Mac because I am not in a design department) and I will tell them to wait for my book thanks to Scrivener.
It is now April 2021 and Scrivener still can’t generate a Kindle mobi file. Still demanding that I upload Kindlegen, which no longer exists. I use your program to write and to publish, but now it’s broken when trying to create files for my biggest customer. Seriously? I have been happy with Scrivener for many years, but this is not good.
Please open a support ticket, here:
literatureandlatte.com/contact-us
Have you installed Kindle Previewer?
Katherine
If you take a moment to search on your issue on this forum (or on Amazon) you will see that KindleGen has been deprecated by Amazon as a stand alone app. It has been discussed MANY times. Download KindlePreviewer which contains a new version.
Also Amazon now prefer to receive books in ePub format instead of .mobi. I’m guessing your biggest customer would hope you are across these now old changes.
If you click the link for KindleGen that Scirvener gives you, it will take you to Amazon’s page that forwards you on to Kindle Previewer. If you download and install that, then read this post and follow the directions: