Amazon FireOs integration

Hi,
Amazon Tablets are running FireOs which is Android based. In fact it is  possible to install Google Play on that tablets and downloading Pushover from Google Play. 
That's what I did and I manage to receive Pushover Text notifications on my Amazon tablet which is great , the messages did not pushed and display over my open app but I was managed to see it in Pushover logs.
My problem is with Audio Notifications. Since, I'm living in Israel all my audio notifications are Hebrew text-to-speech mp3 files since Alexa is not supporting Hebrew language. Unfortunately audio notifications didn't sound via Pushover app. Is there a way to make this works ? Maybe add Pushover to Amazon Store ? 
Any help or idea are welcome . Thank you all in advance...