Solution to EPUBs with video and navigation buttons not working on Android

About 1 year ago I created an App from Indesign (about 300 pages long) and was then asked by the client a few months ago to create a German version. I knew that CC2018 did not have a Folio Builder and so I couldn’t upload the App to Adobe Content Viewer, which was what I was using for client viewing. I recreated the App as an Epub as from what I could see, was the only way to get kind of the same thing. Although the Epub is 400mgb in size the client can use it on Ipad thru iBooks and works fine as long as the iPad is state of the art (mini iPad forget it). However, most of the clients are using PC/Android devices and the Epub3 file is either not readable or if they do manage to get it on an Android phone, for example, none of the interactive buttons work???

Has anyone a solution to this??? Please, I’m totally stuck with an upset client, and Adobe don’t seem to have any solution? The DPS website areas still all work and tell you how to do it in 2014 or earlier (WHY?). If I download the 2014 version and install the necessary plug ins, when I go to Folio Builder it just crashes!!! I’m running High Sierra, is that a problem??