I send my mobi books via email to one of my Kindle devices to the address registered in Manage Your Kindle for that device. I send it from my email address that I've told Amazon is an approved address from which to send books. I then wait a while, usually 10 minutes but it sometimes takes an hour or more, for Amazon to make the book available under Docs.
Once the book is available I download it to all the devices on which I want to read it. When I do that it always syncs just fine.
If I leave out any of those steps it usually doesn't work and it doesn't always tell me it's not going to work.
Barry
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