I have the Blio app on my Kindle Fire and the book I checked out says that TTS is enabled. When I hit the play button it said "no installed TTS voices found" then directs you to the app store to buy one. But it doesn't indicate which one is needed. How do I know which one to download?
Text to speech (TTS) invokes the native Text to speech client for the device. Android an iOS do not have native TTS voices unless you put the device into Accessibility mode (which will read everything). The option to purchase a voice is available in the app and once purchased will work on all TTS enabled content.