Reply To: EPUB fonts not working in kindle mobi.

If you are looking for fixed layout KF8 then CircularFLO https://www.CircularFLO.com is commercial software which creates KF8 directly from InDesign and supports live text without these issues.

I have a feeling that the fonts are working in Kindle Previewer because the fonts are present on the Mac/PC you are running Kindle Previewer on. They then fail when the file is moved to a device without the fonts active.

Have you tried deactivating the fonts on the Mac/PC before opening the eBook? They should still appear when reading the eBook if the fonts are working correctly within it.