[KevinH]

Yes, your screenshots were deleted when I tried to access them as well.

So what we need you to do is go to Sigil's Preferences, and under Appearance Preferences make sure you have checked (enabled) the following:

* BookBrowser should show full paths

Then after saving those Preferences go to Sigil's BookBrowser window (where the files names and logical folders are listed) and write down the full epub relative path to that specific css file and to that specific font file and add that info to this thread.

That way we can validate the relative path from the css file to the that font as the url in your css.

Once we understand that we should be able to tell you how to fix things yourself.