In case of font display problems, it is likely that the client reader does not manage to find the corresponding files on the device where the book is visualized.
In these cases PubCoder provides a Font Replacement Utility.
Such matters may arise not only when the font is actually missing but also when its name is spelled with minor variations
in the CSS.
To be correctly displayed it is necessary that the files corresponding to the fonts requested by the CSS are present and installed on the target device. Most of the times this is not possible, either because the used font is not a system font, but has been bought by the designer, or because the client reader is on a different operating system with different system fonts.
In the case of an import , instead, it often happens that the font names provided by InDesign do not reflect exactly the ones used by the OS and this makes impossible for the client reader to display them correctly.