ePub fixed layout tested with Pagina (app) says.....could not be decrypted

Licensed fonts are encrypted (protected) by InDesign to prevent users from ripping the font files from the epub (which is a zip archive and its file contents can be opened with any zip unarchiver).

Readers must support the encryption method (there are two encryption / obfuscation methods: Adobe and IDPF. If one of these methods to obfuscate is used, software like Pagina may not be able to decrypt the font files.

(PS if you are using InDesign CS6: there was a problem with its epub font encryption, if I recall correctly, which cause errors even in software that supports both encryption methods!)

Anyway, the simple solution is to open your epub in Sigil, right-mouse click each font in the fonts folder and set the Font Obfuscation to "None". Then save the file and test again.

However, this is ILLEGAL unless you have purchased a font license that allows for epub (digital ebook) inclusion or are using a font that is license free.

Minion Pro and Times New Roman PS are not allowed to be embedded in an epub without encrypting them. If this is an issue for you, you will have to replace these with alternate fonts that are allowed and/or licensed to be embedded without encryption.