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LadyKate - when you open the EPUB in the book editor you should be able to see any embedded fonts in the Flies Browser.
If you use Windows:- I keep a copy of the Windows Portable installer on hand, which I can install and use to make sure anomalies such as this are not due to something I've done in preferences etc.
You can create an obfuscated version via the
ScrambleEbook plugin and post it here.
BR