When people face Audio Issues their Amazon fire TV, try these steps:
• If your Fire TV device is connected to an A/V receiver, make sure the receiver is on.
• Go the Settings> Display & Sounds > Audio from the Fire TV menu.
• make sure Dolby Digital Plus of Amazon fire TV is set to OFF.
• If you are using an HDMI cable to connect your Fire TV, unplug it and then reconnect.You may need to try a different HDMI cable.